TextDiagnostic.cpp: Suppress a warning to use ptrdiff_t on i686-clang. [-Wsign-compare]

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174353 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/TextDiagnostic.cpp b/lib/Frontend/TextDiagnostic.cpp
index 4fdc254..28c2a39 100644
--- a/lib/Frontend/TextDiagnostic.cpp
+++ b/lib/Frontend/TextDiagnostic.cpp
@@ -1098,7 +1098,7 @@
   unsigned ColNo = SM.getColumnNumber(FID, FileOffset);
   
   // Arbitrarily stop showing snippets when the line is too long.
-  static const unsigned MaxLineLengthToPrint = 4096;
+  static const ptrdiff_t MaxLineLengthToPrint = 4096;
   if (ColNo > MaxLineLengthToPrint)
     return;