clang-format: Fix __attribute__ being treated as decl name.

[strager]

Summary

__attribute__ was treated as the name of a function
definition, with the tokens in parentheses being the
parameter list. This formats incorrectly with
AlwaysBreakAfterDefinitionReturnType. Fix it by treating
__attribute__ like decltype.

[strager]

Fix commit message for Phabricator.

[strager]

Try to fix binary test problem.

[djasper]

Looks good. Thanks!

[strager]

Please merge for me.

[strager]

Rebase.

[djasper]

Submitted as r241439.

lib/Format/TokenAnnotator.cpp

case tok::kw_for:
         return false;
       break;
     case tok::l_paren:
       if (!parseParens())
         return false;
       if (Line.MustBeDeclaration && Contexts.size() == 1 &&
           !Contexts.back().IsExpression && !Line.startsWith(TT_ObjCProperty) &&
           (!Tok->Previous ||
-           !Tok->Previous->isOneOf(tok::kw_decltype, TT_LeadingJavaAnnotation)))
+           !Tok->Previous->isOneOf(tok::kw_decltype, tok::kw___attribute,
+                                   TT_LeadingJavaAnnotation)))
         Line.MightBeFunctionDecl = true;
       break;
     case tok::l_square:
       if (!parseSquare())
         return false;
       break;
     case tok::l_brace:
       if (!parseBrace())

unittests/Format/FormatTest.cpp

TEST_F(FormatTest, UnderstandsUsesOfStarAndAmp) {
   verifyFormat("A = new SomeType *[Length];", PointerMiddle);
   verifyFormat("T ** t = new T *;", PointerMiddle);
 }
 
 TEST_F(FormatTest, UnderstandsAttributes) {
   verifyFormat("SomeType s __attribute__((unused)) (InitValue);");
   verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa __attribute__((unused))\n"
                "aaaaaaaaaaaaaaaaaaaaaaa(int i);");
+  FormatStyle AfterType = getLLVMStyle();
+  AfterType.AlwaysBreakAfterDefinitionReturnType = FormatStyle::DRTBS_All;
+  verifyFormat("__attribute__((nodebug)) void\n"
+               "foo() {}\n",
+               AfterType);
 }
 
 TEST_F(FormatTest, UnderstandsEllipsis) {
   verifyFormat("int printf(const char *fmt, ...);");
   verifyFormat("template <class... Ts> void Foo(Ts... ts) { Foo(ts...); }");
   verifyFormat("template <class... Ts> void Foo(Ts *... ts) {}");
 
   FormatStyle PointersLeft = getLLVMStyle();