Moved matcher-based capture macros into their own file

- this file excluded from the CATCH_CONFIG_DISABLE_MATCHERS path.
- matchers are always compiled in to the impl file
- _THROWS_WITH macros are still available with matchers disabled - but only the ones that take a string
- tests that use matchers have #ifdefs, so the whole SelfTest project can compile with matchers disable.

projects/SelfTest/ExceptionTests.cpp

@@ -181,6 +181,8 @@ TEST_CASE( "Unexpected exceptions can be translated", "[.][failing][!throws]"  )
         throw double( 3.14 );
 }
 
+#ifndef CATCH_CONFIG_DISABLE_MATCHERS
+
 TEST_CASE( "Exception messages can be tested for", "[!throws]" ) {
     using namespace Catch::Matchers;
     SECTION( "exact match" )
@@ -195,6 +197,8 @@ TEST_CASE( "Exception messages can be tested for", "[!throws]" ) {
     }
 }
 
+#endif
+
 TEST_CASE( "Mismatching exception messages failing the test", "[.][failing][!throws]" ) {
     REQUIRE_THROWS_WITH( thisThrows(), "expected exception" );
     REQUIRE_THROWS_WITH( thisThrows(), "should fail" );