Make vim also output a helpful message in some error cases.

When clang-format encounters a syntax error, it will not format that
line; we're now using the same mechanism we're already using in emacs to
show a helpful error message to the user.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@238823 91177308-0d34-0410-b5e6-96231b3b80d8

Author: r4nt

tools/clang-format/clang-format.py

@@ -85,6 +85,8 @@ def main():
     for op in reversed(sequence.get_opcodes()):
       if op[0] is not 'equal':
         vim.current.buffer[op[1]:op[2]] = lines[op[3]:op[4]]
+    if output['IncompleteFormat']:
+      print 'clang-format: incomplete (syntax errors)'
     vim.command('goto %d' % (output['Cursor'] + 1))
 
 main()