clang-format: Format typed enums with nested names.

The explicit type specified for an enum can actually have a nested name
specifier.

This fixes llvm.org/PR17125.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190208 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index ae35ccc..79dbad7 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -1591,6 +1591,10 @@
                "  A,\n"
                "  B\n"
                "};");
+  verifyFormat("enum X : std::uint32_t {\n"
+               "  A,\n"
+               "  B\n"
+               "};");
 }
 
 TEST_F(FormatTest, FormatsBitfields) {