Don't assume size_t is unsigned long long.

Fixes a -Woverflow warning from gcc when building for 32-bit platforms.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156313 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/SourceMgr.cpp b/lib/Support/SourceMgr.cpp
index 5fa987b..37a9d8f 100644
--- a/lib/Support/SourceMgr.cpp
+++ b/lib/Support/SourceMgr.cpp
@@ -121,7 +121,7 @@
   Cache.LineNoOfQuery = LineNo;
   
   size_t NewlineOffs = StringRef(BufStart, Ptr-BufStart).find_last_of("\n\r");
-  if (NewlineOffs == StringRef::npos) NewlineOffs = ~0ULL;
+  if (NewlineOffs == StringRef::npos) NewlineOffs = ~(size_t)0;
   return std::make_pair(LineNo, Ptr-BufStart-NewlineOffs);
 }
 
@@ -358,5 +358,3 @@
   
   S << '\n';
 }
-
-