More improvements to GDBStub (#653)

* More improvements to GDBStub
- Debugging of threads should work correctly with source and assembly level stepping and modifying registers and memory, meaning threads and callstacks are fully clickable in VS.
- List of modules is available to the client, with assumption that .nro and .nso are backed up by an .elf with symbols, while deconstructed ROMs keep N names.
- Initial support for floating point registers.

* Tidy up as requested in PR feedback

* Tidy up as requested in PR feedback

src/common/string_util.cpp

@@ -134,7 +134,7 @@ bool SplitPath(const std::string& full_path, std::string* _pPath, std::string* _
     size_t dir_end = full_path.find_last_of("/"
 // windows needs the : included for something like just "C:" to be considered a directory
 #ifdef _WIN32
-                                            ":"
+                                            "\\:"
 #endif
     );
     if (std::string::npos == dir_end)