Clear all the linetable state in clear(), fixing problems

with "clang t.i s.i" where the .i files contain line markers.
rdar://6667812

llvm-svn: 66619

clang/lib/Basic/SourceManager.cpp

@@ -129,6 +129,7 @@ public:
   void clear() {
     FilenameIDs.clear();
     FilenamesByID.clear();
+    LineEntries.clear();
   }
   
   ~LineTableInfo() {}