Execute "sign place" with C lang

Fixes https://github.com/mhinz/vim-signify/issues/293

autoload/sy/fold.vim

@@ -88,12 +88,7 @@ endfunction
 
 " Function: s:get_lines {{{1
 function! s:get_lines() abort
-  let lang = v:lang
+  let signlist = sy#util#execute('sign place buffer='. b:sy.buffer)
-  language message C
-  redir => signlist
-    silent! execute 'sign place buffer='. b:sy.buffer
-  redir END
-  silent! execute 'language message' lang
 
   let lines = []
   for line in split(signlist, '\n')[2:]

autoload/sy/sign.vim

@@ -24,9 +24,7 @@ function! sy#sign#get_current_signs(sy) abort
   let a:sy.internal = {}
   let a:sy.external = {}
 
-  redir => signlist
+  let signlist = sy#util#execute('sign place buffer='. a:sy.buffer)
-    silent! execute 'sign place buffer='. a:sy.buffer
-  redir END
 
   for signline in split(signlist, '\n')[2:]
     let tokens = matchlist(signline, '\v^\s+\S+\=(\d+)\s+\S+\=(\d+)\s+\S+\=(.*)$')

autoload/sy/util.vim

@@ -97,3 +97,13 @@ function! sy#util#return_if_no_changes() abort
   endif
   return ''
 endfunction
+
+" Function: #execute {{{1
+function! sy#util#execute(cmd) abort
+  let lang = v:lang
+  redir => output
+    silent! execute a:cmd
+  redir END
+  silent! execute 'language message' lang
+  return output
+endfunction