clang-format: Fix crasher when a UTF8 character is found in an escape
sequence. Discovered by the fuzzer.

llvm-svn: 242738
diff --git a/clang/lib/Format/Encoding.h b/clang/lib/Format/Encoding.h
index 766d292..592d720 100644
--- a/clang/lib/Format/Encoding.h
+++ b/clang/lib/Format/Encoding.h
@@ -135,7 +135,7 @@
         ++I;
       return I;
     }
-    return 2;
+    return 1 + getNumBytesForUTF8(Text[1]);
   }
 }