clang-format: Allow unbroken ::: in inline assembly.

Before:
  asm volatile("nop" :: : "memory");

After:
  asm volatile("nop" ::: "memory");

Patch by Eugene Toder. Thank you.

llvm-svn: 217883
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 4b0791d..7da0b53 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -2105,6 +2105,7 @@
 
 TEST_F(FormatTest, FormatsInlineASM) {
   verifyFormat("asm(\"xyz\" : \"=a\"(a), \"=d\"(b) : \"a\"(data));");
+  verifyFormat("asm(\"nop\" ::: \"memory\");");
   verifyFormat(
       "asm(\"movq\\t%%rbx, %%rsi\\n\\t\"\n"
       "    \"cpuid\\n\\t\"\n"