Implement crash handling on Linux

This will allow us to generate crash dumps and have users report
crashes.

BuildConfig.h

@@ -61,10 +61,14 @@ public:
 
 	/// The commit hash of this build
 	QString GIT_COMMIT;
+	const char* GIT_COMMIT_CSTR;
 
 	/// This is printed on start to standard output
 	QString VERSION_STR;
 
+	/// Version string as a char string. Used by the crash handling system to avoid touching heap memory.
+	const char* VERSION_CSTR;
+
 	/**
 	 * This is used to fetch the news RSS feed.
 	 * It defaults in CMakeLists.txt to "http://multimc.org/rss.xml"