Fix the location of the fixit for -Wnewline-eof.

It turns out SourceManager treating the "one-past-the-end" location as invalid,
but then failing to set the invalid flag properly.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158699 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 66b06ef..24bd519 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -1015,9 +1015,10 @@
   if (MyInvalid)
     return 1;
 
-  if (FilePos >= MemBuf->getBufferSize()) {
+  // It is okay to request a position just past the end of the buffer.
+  if (FilePos > MemBuf->getBufferSize()) {
     if (Invalid)
-      *Invalid = MyInvalid;
+      *Invalid = true;
     return 1;
   }