Transition from QtCore to stdc++ / STL / boost

This looks like a pretty major change, but in reality,
80% of it is just renames of types and corresponding
methods.

The config parsing code has been completely replaced
with a boost::program_options based version. This
means that the config file format slightly changed
(checkout the updated README).

I still expect there to be bugs / unforseen events.
Those should be fixed in follow up commits.

Also, finally reverted back to using pkg-config to
locate and link libruby. Yay for less hacks!

src/eventthread.h

@@ -30,7 +30,7 @@
 #include <SDL_mouse.h>
 #include <SDL_mutex.h>
 
-#include <QByteArray>
+#include <string>
 
 #include <stdint.h>
 
@@ -173,7 +173,7 @@ struct RGSSThreadData
 
 	Config config;
 
-	QByteArray rgssErrorMsg;
+	std::string rgssErrorMsg;
 
 	volatile bool rqScreenshot;