Fix another escaping issue, with a global escape method ref #168

Another issue with escape problem. It was finally the same culprit.

match() function take a pattern as a paramter. If a:selection[0], the
hunk title, contains any regex special character, it goes wild.

It seems safer to escape with special character \V (very nomagic)
instead of adding regularly special characters to escape() function.

plugin/magit.vim

@@ -965,7 +965,7 @@ function! magit#stage_block(selection, discard) abort
 	" find current hunk position in file matching against current selection
 	" header
 	try
-		let hunk_id = match(map(deepcopy(file.get_hunks()), 'v:val.header'), escape(a:selection[0], '~*'))
+		let hunk_id = match(map(deepcopy(file.get_hunks()), 'v:val.header'), "\\V" . a:selection[0])
 	catch /^Vim\%((\a\+)\)\=:E874/
 		echoerr "Escape issue with '" . a:selection[0] ."'"
 		return