clang-format: fix for \r\r\n produced in multiline block comments

Patch by Christopher Olsen. Thank you!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193678 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/BreakableToken.cpp b/lib/Format/BreakableToken.cpp
index cbc50f5..9747578 100644
--- a/lib/Format/BreakableToken.cpp
+++ b/lib/Format/BreakableToken.cpp
@@ -25,13 +25,14 @@
 namespace clang {
 namespace format {
 
-static const char *const Blanks = " \t\v\f";
+static const char *const Blanks = " \t\v\f\r";
 static bool IsBlank(char C) {
   switch (C) {
   case ' ':
   case '\t':
   case '\v':
   case '\f':
+  case '\r':
     return true;
   default:
     return false;