[clang-format] Ensure ObjC selectors with 0 args are annotated correctly

Summary:
Previously, clang-format would incorrectly annotate 0-argument
Objective-C selector names as TT_TrailingAnnotation:

```
% echo "-(void)foo;" > /tmp/test.m
% ./bin/clang-format -debug /tmp/test.m
Language: Objective-C
----
Line(0, FSC=0): minus[T=68, OC=0] l_paren[T=68, OC=1] void[T=68, OC=2]
r_paren[T=68, OC=6] identifier[T=68, OC=7] semi[T=68, OC=10]
Line(0, FSC=0): eof[T=68, OC=0]
Run 0...
AnnotatedTokens(L=0):
 M=0 C=0 T=ObjCMethodSpecifier S=1 B=0 BK=0 P=0 Name=minus L=1 PPK=2
 FakeLParens= FakeRParens=0 Text='-'
 M=0 C=1 T=Unknown S=1 B=0 BK=0 P=33 Name=l_paren L=3 PPK=2
 FakeLParens= FakeRParens=0 Text='('
 M=0 C=1 T=Unknown S=0 B=0 BK=0 P=140 Name=void L=7 PPK=2 FakeLParens=
 FakeRParens=0 Text='void'
 M=0 C=0 T=CastRParen S=0 B=0 BK=0 P=43 Name=r_paren L=8 PPK=2
 FakeLParens= FakeRParens=0 Text=')'
 M=0 C=1 T=TrailingAnnotation S=0 B=0 BK=0 P=120 Name=identifier L=11
 PPK=2 FakeLParens= FakeRParens=0 Text='foo'
 M=0 C=0 T=Unknown S=0 B=0 BK=0 P=23 Name=semi L=12 PPK=2 FakeLParens=
 FakeRParens=0 Text=';'
```

This caused us to incorrectly indent 0-argument wrapped selectors
when Style.IndentWrappedFunctionNames was false, as we thought
the 0-argument ObjC selector name was actually a trailing
annotation (which is always indented).

This diff fixes the issue and adds tests.

Test Plan: New tests added. Confirmed tests failed before diff.
  After diff, tests passed. Ran tests with:
  % make -j12 FormatTests &&
  ./tools/clang/unittests/Format/FormatTests

Reviewers: djasper, jolesiak

Reviewed By: djasper, jolesiak

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D44996

llvm-svn: 329297