FileSearch: Don't use RegExs, just do string comparisons.

Nothing used the RegEx feature of FileSearch, and GCC < 4.9
doesn't support C++11 RegEx properly, so get rid of it.

Source/Core/DolphinWX/Config/InterfaceConfigPane.cpp

@@ -162,7 +162,7 @@ void InterfaceConfigPane::LoadGUIValues()
 
 void InterfaceConfigPane::LoadThemes()
 {
-	auto sv = DoFileSearch({"*"}, {
+	auto sv = DoFileSearch({""}, {
 		File::GetUserPath(D_THEMES_IDX),
 		File::GetSysDirectory() + THEMES_DIR
 	}, /*recursive*/ false);