Make string pointer const.

llvm-svn: 185296
diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
index e340f4f..d48c3cb 100644
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -26,7 +26,7 @@
 namespace format {
 namespace {
 
-static const char *Blanks = " \t\v\f";
+static const char *const Blanks = " \t\v\f";
 static bool IsBlank(char C) {
   switch (C) {
     case ' ':