doc: Remove references to the Mac GUI #4016

We don't support it.

runtime/doc/editing.txt

@@ -1145,7 +1145,7 @@ If you want to always use ":confirm", set the 'confirm' option.
 			|:diffsplit|, |:diffpatch|, |:pedit|, |:redir|,
 			|:source|, |:update|, |:visual|, |:vsplit|,
 			and |:qall| if 'confirm' is set.
-			{only in Win32 and Mac GUI}
+			{only in Win32 GUI}
 			When ":browse" is not possible you get an error
 			message.  If the |+browse| feature is missing or the
 			{command} doesn't support browsing, the {command} is

runtime/doc/eval.txt

@@ -2563,9 +2563,9 @@ confirm({msg} [, {choices} [, {default} [, {type}]]])
 		{default} is omitted, 1 is used.
 
 		The optional {type} argument gives the type of dialog.  This
-		is only used for the icon of the Mac and Win32 GUI.  It
-		can be one of these values: "Error", "Question", "Info",
-		"Warning" or "Generic".  Only the first character is relevant.
+		is only used for the icon of the Win32 GUI.  It can be one of
+		these values: "Error", "Question", "Info", "Warning" or
+		"Generic".  Only the first character is relevant.
 		When {type} is omitted, "Generic" is used.
 
 		If the user aborts the dialog by pressing <Esc>, CTRL-C,
@@ -6993,7 +6993,6 @@ fname_case		Case in file names matters (for Windows this is not
 folding			Compiled with |folding| support.
 gettext			Compiled with message translation |multi-lang|
 gui			Compiled with GUI enabled.
-gui_mac			Compiled with Macintosh GUI.
 gui_running		Vim is running in the GUI, or it will start soon.
 gui_win32		Compiled with MS Windows Win32 GUI.
 iconv			Can use iconv() for conversion.

runtime/doc/repeat.txt

@@ -390,7 +390,7 @@ To enter debugging mode use one of these methods:
    useful to find out what is happening when Vim is starting up.  A side
    effect is that Vim will switch the terminal mode before initialisations
    have finished, with unpredictable results.
-   For a GUI-only version (Windows, Macintosh) the debugging will start as
+   For a GUI-only version (Windows) the debugging will start as
    soon as the GUI window has been opened.  To make this happen early, add a
    ":gui" command in the vimrc file.
 								*:debug*

runtime/doc/vi_diff.txt

@@ -77,7 +77,7 @@ Graphical User Interface (GUI).				|gui|
 	Included support for GUI: menu's, mouse, scrollbars, etc.  You can
 	define your own menus.  Better support for CTRL/SHIFT/ALT keys in
 	combination with special keys and mouse.  Supported for various
-	platforms such as Win32 and Macintosh.
+	platforms such as Win32.
 
 Multiple windows and buffers.				|windows.txt|
 	Vim can split the screen into several windows, each editing a