Fix visual placeholder in legacy parser

The fix for #177 only handled the case where a visual placeholder was on
a line with an indent. With this commit, all cases should be handled.
Hopefully.

See #233

autoload/snipmate/legacy.vim

@@ -12,8 +12,7 @@ function! snipmate#legacy#process_snippet(snip) abort
 	else
 		let visual = ''
 	endif
-	let snippet = substitute(snippet, '\n\(\t\+\).\{-\}\zs{VISUAL}',
-				\ substitute(escape(visual, '%\'), "\n", "\n\\\\1", 'g'), 'g')
+        let snippet = s:substitute_visual(snippet, visual)
 
 	" Evaluate eval (`...`) expressions.
 	" Backquotes prefixed with a backslash "\" are ignored.
@@ -118,6 +117,16 @@ function! snipmate#legacy#build_stops(snip, lnum, col, indent) abort
 	return [stops, i + 1]
 endfunction
 
+function! s:substitute_visual(snippet, visual) abort
+    let lines = []
+    for line in split(a:snippet, "\n")
+        let indent = matchstr(line, '^\t\+')
+        call add(lines, substitute(line, '{VISUAL}',
+                    \ substitute(escape(a:visual, '%\'), "\n", "\n" . indent, 'g'), 'g'))
+    endfor
+    return join(lines, "\n")
+endfunction
+
 " Counts occurences of haystack in needle
 function! s:count(haystack, needle) abort
 	let counter = 0