patch 8.1.2096: too many #ifdefs

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_COMMENTS.

runtime/doc/change.txt

@@ -1618,8 +1618,6 @@ By default, "b:#" is included.  This means that a line that starts with
 "#include" is not recognized as a comment line.  But a line that starts with
 "# define" is recognized.  This is a compromise.
 
-{not available when compiled without the |+comments| feature}
-
 							*fo-table*
 You can use the 'formatoptions' option  to influence how Vim formats text.
 'formatoptions' is a string that can contain any of the letters below.  The

runtime/doc/options.txt

@@ -1685,8 +1685,6 @@ A jump table for the options with a short description can be found at |Q_op|.
 'comments' 'com'	string	(default
 				"s1:/*,mb:*,ex:*/,://,b:#,:%,:XCOMM,n:>,fb:-")
 			local to buffer
-			{not available when compiled without the |+comments|
-			feature}
 	A comma separated list of strings that can start a comment line.  See
 	|format-comments|.  See |option-backslash| about using backslashes to
 	insert a space.

runtime/doc/various.txt

@@ -1,4 +1,4 @@
-*various.txt*   For Vim version 8.1.  Last change: 2019 Sep 04
+*various.txt*   For Vim version 8.1.  Last change: 2019 Sep 28
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -337,7 +337,7 @@ N  *+clientserver*	Unix and Win32: Remote invocation |clientserver|
 T  *+cmdline_compl*	command line completion |cmdline-completion|
 S  *+cmdline_hist*	command line history |cmdline-history|
 N  *+cmdline_info*	|'showcmd'| and |'ruler'|
-N  *+comments*		|'comments'| support
+T  *+comments*		|'comments'| support
 B  *+conceal*		"conceal" support, see |conceal| |:syn-conceal| etc.
 N  *+cryptv*		encryption support |encryption|
 B  *+cscope*		|cscope| support