[Support] Use range-based for loop. NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@259763 91177308-0d34-0410-b5e6-96231b3b80d8

Author: topperc

lib/Support/raw_ostream.cpp

@@ -181,9 +181,7 @@ raw_ostream &raw_ostream::write_hex(unsigned long long N) {
 
 raw_ostream &raw_ostream::write_escaped(StringRef Str,
                                         bool UseHexEscapes) {
-  for (unsigned i = 0, e = Str.size(); i != e; ++i) {
-    unsigned char c = Str[i];
-
+  for (unsigned char c : Str) {
     switch (c) {
     case '\\':
       *this << '\\' << '\\';