Fixes PR14811: Crash when formatting some macros

A preprocessor directive cannot be started while we're parsing one.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171635 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/UnwrappedLineParser.cpp b/lib/Format/UnwrappedLineParser.cpp
index 04d1b36..c1bafa9 100644
--- a/lib/Format/UnwrappedLineParser.cpp
+++ b/lib/Format/UnwrappedLineParser.cpp
@@ -469,7 +469,7 @@
 
 void UnwrappedLineParser::readToken() {
   FormatTok = Tokens->getNextToken();
-  while (FormatTok.Tok.is(tok::hash)) {
+  while (!Line.InPPDirective && FormatTok.Tok.is(tok::hash)) {
     // FIXME: This is incorrect - the correct way is to create a
     // data structure that will construct the parts around the preprocessor
     // directive as a structured \c UnwrappedLine.