Removed three useless/wrong/etc. function prototypes for when

libgtkglext isn't installed...

desmume/src/gtk-glade/callbacks_IO.c

@@ -80,9 +80,6 @@ void black_screen () {
 // else see gdk_gl.c / gdk_gl.h
 BOOL my_gl_Begin (int screen) { return FALSE; }
 void my_gl_End (int screen) {}
-void init_GL_capabilities() {}
-void init_GL(GtkWidget * widget, ...) {}
-void reshape (GtkWidget * widget, ...) {}
 
 int has_pix_col_map=0;
 u32 pix_col_map[0x8000];