Rewrite FileSearch and improve ScanDirectoryTree.

- FileSearch is now just one function, and it converts the original glob
  into a regex on all platforms rather than relying on native Windows
  pattern matching on there and a complete hack elsewhere.  It now
  supports recursion out of the box rather than manually expanding
  into a full list of directories in multiple call sites.

  - This adds a GCC >= 4.9 dependency due to older versions having
  outright broken <regex>.  MSVC is fine with it.

- ScanDirectoryTree returns the parent entry rather than filling parts
  of it in via reference.  The count is now stored in the entry like it
  was for subdirectories.

- .glsl file search is now done with DoFileSearch.

- IOCTLV_READ_DIR now uses ScanDirectoryTree directly and sorts the
  results after replacements for better determinism.

Source/Core/DiscIO/VolumeDirectory.h

@@ -75,12 +75,12 @@ private:
 	void Write32(u32 data, u32 offset, std::vector<u8>* const buffer);
 
 	// FST creation
-	void WriteEntryData(u32& entryOffset, u8 type, u32 nameOffset, u64 dataOffset, u32 length);
+	void WriteEntryData(u32& entryOffset, u8 type, u32 nameOffset, u64 dataOffset, u64 length);
 	void WriteEntryName(u32& nameOffset, const std::string& name);
 	void WriteEntry(const File::FSTEntry& entry, u32& fstOffset, u32& nameOffset, u64& dataOffset, u32 parentEntryNum);
 
 	// returns number of entries found in _Directory
-	u32 AddDirectoryEntries(const std::string& _Directory, File::FSTEntry& parentEntry);
+	u64 AddDirectoryEntries(const std::string& _Directory, File::FSTEntry& parentEntry);
 
 	std::string m_rootDirectory;