Standardize header names and file locations

This is both a really big and a really small commit. It is small in
that it only contains renaming, moving and modification of include
directives caused by this.

It is really big in the obvious way of touching something like 200
files.

The new rules for naming files is simple: headers use the `.hpp`
extension. The rules for physical file layout is still kinda in
progress, but the basics are also simple:
 * Significant parts of functionality get their own subfolder
   * Benchmarking is in `catch2/benchmark`
   * Matchers are in `catch2/matchers`
   * Generators are in `catch2/generators`
   * Reporters are in `catch2/reporters`
   * Baseline testing facilities are in `catch2/`
 * Various top level folders also contain `internal` subfolder,
   with files that users probably do not want to include directly,
   at least not until they have to write something like their own
   reporter.
    * The exact files in these subfolders is likely to change later
      on

Note that while some includes were cleaned up in this commit, it
is only the low hanging fruit and further cleanup using automatic
tooling will happen later.

Also note that various include guards, copyright notices and file
headers will also be standardized later, rather than in this commit.

src/catch2/internal/catch_assertionhandler.cpp

@@ -0,0 +1,123 @@
+/*
+ *  Created by Phil on 8/8/2017.
+ *  Copyright 2017 Two Blue Cubes Ltd. All rights reserved.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include <catch2/internal/catch_assertionhandler.hpp>
+#include <catch2/catch_assertion_result.hpp>
+#include <catch2/interfaces/catch_interfaces_runner.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_debugger.hpp>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
+#include <catch2/internal/catch_capture_matchers.hpp>
+#include <catch2/internal/catch_run_context.hpp>
+#include <catch2/matchers/catch_matchers_string.hpp>
+
+namespace Catch {
+
+    namespace {
+        auto operator <<( std::ostream& os, ITransientExpression const& expr ) -> std::ostream& {
+            expr.streamReconstructedExpression( os );
+            return os;
+        }
+    }
+
+    LazyExpression::LazyExpression( bool isNegated )
+    :   m_isNegated( isNegated )
+    {}
+
+    LazyExpression::LazyExpression( LazyExpression const& other ) : m_isNegated( other.m_isNegated ) {}
+
+    LazyExpression::operator bool() const {
+        return m_transientExpression != nullptr;
+    }
+
+    auto operator << ( std::ostream& os, LazyExpression const& lazyExpr ) -> std::ostream& {
+        if( lazyExpr.m_isNegated )
+            os << "!";
+
+        if( lazyExpr ) {
+            if( lazyExpr.m_isNegated && lazyExpr.m_transientExpression->isBinaryExpression() )
+                os << "(" << *lazyExpr.m_transientExpression << ")";
+            else
+                os << *lazyExpr.m_transientExpression;
+        }
+        else {
+            os << "{** error - unchecked empty expression requested **}";
+        }
+        return os;
+    }
+
+    AssertionHandler::AssertionHandler
+        (   StringRef const& macroName,
+            SourceLineInfo const& lineInfo,
+            StringRef capturedExpression,
+            ResultDisposition::Flags resultDisposition )
+    :   m_assertionInfo{ macroName, lineInfo, capturedExpression, resultDisposition },
+        m_resultCapture( getResultCapture() )
+    {}
+
+    void AssertionHandler::handleExpr( ITransientExpression const& expr ) {
+        m_resultCapture.handleExpr( m_assertionInfo, expr, m_reaction );
+    }
+    void AssertionHandler::handleMessage(ResultWas::OfType resultType, StringRef const& message) {
+        m_resultCapture.handleMessage( m_assertionInfo, resultType, message, m_reaction );
+    }
+
+    auto AssertionHandler::allowThrows() const -> bool {
+        return getCurrentContext().getConfig()->allowThrows();
+    }
+
+    void AssertionHandler::complete() {
+        setCompleted();
+        if( m_reaction.shouldDebugBreak ) {
+
+            // If you find your debugger stopping you here then go one level up on the
+            // call-stack for the code that caused it (typically a failed assertion)
+
+            // (To go back to the test and change execution, jump over the throw, next)
+            CATCH_BREAK_INTO_DEBUGGER();
+        }
+        if (m_reaction.shouldThrow) {
+#if !defined(CATCH_CONFIG_DISABLE_EXCEPTIONS)
+            throw Catch::TestFailureException();
+#else
+            CATCH_ERROR( "Test failure requires aborting test!" );
+#endif
+        }
+    }
+    void AssertionHandler::setCompleted() {
+        m_completed = true;
+    }
+
+    void AssertionHandler::handleUnexpectedInflightException() {
+        m_resultCapture.handleUnexpectedInflightException( m_assertionInfo, Catch::translateActiveException(), m_reaction );
+    }
+
+    void AssertionHandler::handleExceptionThrownAsExpected() {
+        m_resultCapture.handleNonExpr(m_assertionInfo, ResultWas::Ok, m_reaction);
+    }
+    void AssertionHandler::handleExceptionNotThrownAsExpected() {
+        m_resultCapture.handleNonExpr(m_assertionInfo, ResultWas::Ok, m_reaction);
+    }
+
+    void AssertionHandler::handleUnexpectedExceptionNotThrown() {
+        m_resultCapture.handleUnexpectedExceptionNotThrown( m_assertionInfo, m_reaction );
+    }
+
+    void AssertionHandler::handleThrowingCallSkipped() {
+        m_resultCapture.handleNonExpr(m_assertionInfo, ResultWas::Ok, m_reaction);
+    }
+
+    // This is the overload that takes a string and infers the Equals matcher from it
+    // The more general overload, that takes any string matcher, is in catch_capture_matchers.cpp
+    void handleExceptionMatchExpr( AssertionHandler& handler, std::string const& str, StringRef const& matcherString  ) {
+        handleExceptionMatchExpr( handler, Matchers::Equals( str ), matcherString );
+    }
+
+} // namespace Catch