patch 8.0.1236: Mac features are confusing

Problem:    Mac features are confusing.
Solution:   Make feature names more consistent, add "osxdarwin". Rename
            feature flags, cleanup Mac code. (Kazunobu Kuriyama, closes #2178)
diff --git a/src/globals.h b/src/globals.h
index 31bb1bd..3183632 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1425,7 +1425,7 @@
 #if defined(FEAT_GUI) && defined(FEAT_XFONTSET)
 EXTERN char_u e_fontset[]	INIT(= N_("E234: Unknown fontset: %s"));
 #endif
-#if defined(FEAT_GUI_X11) || defined(FEAT_GUI_GTK) || defined(MACOS) \
+#if defined(FEAT_GUI_X11) || defined(FEAT_GUI_GTK) || defined(FEAT_GUI_MAC) \
 	|| defined(FEAT_GUI_PHOTON) || defined(FEAT_GUI_MSWIN)
 EXTERN char_u e_font[]		INIT(= N_("E235: Unknown font: %s"));
 #endif
@@ -1545,7 +1545,7 @@
 EXTERN char_u e_sandbox[]	INIT(= N_("E48: Not allowed in sandbox"));
 #endif
 EXTERN char_u e_secure[]	INIT(= N_("E523: Not allowed here"));
-#if defined(AMIGA) || defined(MACOS) || defined(MSWIN)  \
+#if defined(AMIGA) || defined(MACOS_X) || defined(MSWIN)  \
 	|| defined(UNIX) || defined(VMS)
 EXTERN char_u e_screenmode[]	INIT(= N_("E359: Screen mode setting not supported"));
 #endif
@@ -1592,7 +1592,7 @@
 #endif
 EXTERN char_u e_dirnotf[]	INIT(= N_("E919: Directory not found in '%s': \"%s\""));
 
-#ifdef MACOS_X_UNIX
+#ifdef FEAT_GUI_MAC
 EXTERN short disallow_gui	INIT(= FALSE);
 #endif