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/Common/FileSearch.h

@@ -7,18 +7,5 @@
 #include <string>
 #include <vector>
 
-class CFileSearch
-{
-public:
-	typedef std::vector<std::string>XStringVector;
-
-	CFileSearch(const XStringVector& _rSearchStrings, const XStringVector& _rDirectories);
-	const XStringVector& GetFileNames() const;
-
-private:
-
-	void FindFiles(const std::string& _searchString, const std::string& _strPath);
-
-	XStringVector m_FileNames;
-};
-
+std::vector<std::string> DoFileSearch(const std::vector<std::string>& globs, const std::vector<std::string>& directories, bool recursive = false);
+std::vector<std::string> FindSubdirectories(const std::vector<std::string>& directories, bool recursive);