Add syntax files from upstream vim repository

autoload/contextcomplete.vim

@@ -0,0 +1,29 @@
+if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'vim') == -1
+  
+" Language:           ConTeXt typesetting engine
+" Maintainer:         Nicola Vitacolonna <nvitacolonna@gmail.com>
+" Latest Revision:    2016 Oct 15
+
+let s:keepcpo= &cpo
+set cpo&vim
+
+" Complete keywords in MetaPost blocks
+function! contextcomplete#Complete(findstart, base)
+  if a:findstart == 1
+    if len(synstack(line('.'), 1)) > 0 &&
+          \ synIDattr(synstack(line('.'), 1)[0], "name") ==# 'contextMPGraphic'
+      return syntaxcomplete#Complete(a:findstart, a:base)
+    else
+      return -3
+    endif
+  else
+    return syntaxcomplete#Complete(a:findstart, a:base)
+  endif
+endfunction
+
+let &cpo = s:keepcpo
+unlet s:keepcpo
+
+" vim: sw=2 fdm=marker
+
+endif