contrib/vimrc: detect more C-like files

Currently this script doesn't set the indentation style for the standard
library headers under libstdc++/ because they lack a file extension.
But they do have a modeline, so the file type is still set appropriately
by Vim.  So by inspecting &filetype, we can also detect these standard
library headers as C-like files.

contrib/ChangeLog:

	* vimrc (SetStyle): Also inspect &filetype to determine whether
	a file is C-like.

contrib/vimrc

@@ -45,7 +45,7 @@ function! SetStyle()
     setlocal textwidth=80
   endif
   setlocal formatoptions-=ro formatoptions+=cqlt
-  if index(l:c_exts, l:ext) != -1
+  if index(l:c_exts, l:ext) != -1 || &filetype == "c" || &filetype == "cpp"
     setlocal cindent
     setlocal cinoptions=>4,n-2,{2,^-2,:2,=2,g0,f0,h2,p4,t0,+2,(0,u0,w1,m0
   endif