patch 8.2.1422: the Mac GUI implementation is outdated

Problem:    The Mac GUI implementation is outdated and probably doesn't even
            work.
Solution:   Remove the Mac GUI code.  The MacVim project provides the
            supported Vim GUI version.
diff --git a/src/globals.h b/src/globals.h
index 72b8a1e..f64a874 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1569,7 +1569,7 @@
 #if defined(FEAT_GUI) && defined(FEAT_XFONTSET)
 EXTERN char e_fontset[]	INIT(= N_("E234: Unknown fontset: %s"));
 #endif
-#if defined(FEAT_GUI_X11) || defined(FEAT_GUI_GTK) || defined(FEAT_GUI_MAC) \
+#if defined(FEAT_GUI_X11) || defined(FEAT_GUI_GTK) \
 	|| defined(FEAT_GUI_PHOTON) || defined(FEAT_GUI_MSWIN) || defined(FEAT_GUI_HAIKU)
 EXTERN char e_font[]		INIT(= N_("E235: Unknown font: %s"));
 #endif
@@ -1806,10 +1806,6 @@
 EXTERN char e_alloc_color[]	INIT(= N_("E254: Cannot allocate color %s"));
 #endif
 
-#ifdef FEAT_GUI_MAC
-EXTERN short disallow_gui	INIT(= FALSE);
-#endif
-
 EXTERN char top_bot_msg[] INIT(= N_("search hit TOP, continuing at BOTTOM"));
 EXTERN char bot_top_msg[] INIT(= N_("search hit BOTTOM, continuing at TOP"));