- moved all exception handling out of the backends

The main catch is now in D_DoomMain, only calling platform specific functions to handle the output for the error.

As a nice side effect, -norun can now be done without an exception, just by exiting D_DoomMain with a special exit code.

src/posix/sdl/i_system.cpp

@@ -103,7 +103,6 @@ void I_Init (void)
 // I_Error
 //
 extern FILE *Logfile;
-bool gameisdead;
 
 #ifdef __APPLE__
 void Mac_I_FatalError(const char* errortext);