Add static cast to unsigned char whenever a character classification function is called with a signed char argument, in order to avoid assertions in Windows Debug configuration.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175006 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/FileUtilities.cpp b/lib/Support/FileUtilities.cpp
index fc8a2f3..4d7b239 100644
--- a/lib/Support/FileUtilities.cpp
+++ b/lib/Support/FileUtilities.cpp
@@ -87,9 +87,9 @@
 
   // If one of the positions is at a space and the other isn't, chomp up 'til
   // the end of the space.
-  while (isspace(*F1P) && F1P != F1End)
+  while (isspace(static_cast<unsigned char>(*F1P)) && F1P != F1End)
     ++F1P;
-  while (isspace(*F2P) && F2P != F2End)
+  while (isspace(static_cast<unsigned char>(*F2P)) && F2P != F2End)
     ++F2P;
 
   // If we stop on numbers, compare their difference.