clang-format-diff.py: add the OpenCL file extension

It's handled correctly as a C-family language.

llvm-svn: 197542
diff --git a/clang/tools/clang-format/clang-format-diff.py b/clang/tools/clang-format/clang-format-diff.py
index b914c37..5cece8d 100755
--- a/clang/tools/clang-format/clang-format-diff.py
+++ b/clang/tools/clang-format/clang-format-diff.py
@@ -47,7 +47,7 @@
                       help='custom pattern selecting file paths to reformat '
                       '(case sensitive, override -iregex)')
   parser.add_argument('-iregex', metavar='PATTERN', default=
-                      r'.*\.(cpp|cc|c\+\+|cxx|c|h|hpp|m|mm|inc|js)',
+                      r'.*\.(cpp|cc|c\+\+|cxx|c|cl|h|hpp|m|mm|inc|js)',
                       help='custom pattern selecting file paths to reformat '
                       '(case insensitive, override -regex)')
   parser.add_argument(