[clang-format/ObjC] Fix NS_SWIFT_NAME(foo(bar:baz:)) after ObjC method decl

Summary:
In D44638, I partially fixed `NS_SWIFT_NAME(foo(bar:baz:))`-style
annotations on C functions, but didn't add a test for Objective-C
method declarations.

For ObjC method declarations which are annotated with `NS_SWIFT_NAME(...)`,
we currently fail to annotate the final component of the selector
name as `TT_SelectorName`.

Because the token type is left unknown, clang-format will happily
cause a compilation error when it changes the following:

```
@interface Foo
- (void)doStuffWithFoo:(id)name
                   bar:(id)bar
                   baz:(id)baz
    NS_SWIFT_NAME(doStuff(withFoo:bar:baz:));
@end
```

to:

```
@interface Foo
- (void)doStuffWithFoo:(id)name
                   bar:(id)bar
                   baz:(id)baz
    NS_SWIFT_NAME(doStuff(withFoo:bar:baz
:));
@end
```

(note the linebreak before the final `:`).

The logic which decides whether or not to annotate the token before a
`:` with `TT_SelectorName` is pretty fragile, and has to handle some
pretty odd cases like pair-parameters:

```
[I drawRectOn:surface ofSize:aa:bbb atOrigin:cc:dd];
```

So, to minimize the effect of this change, I decided to only annotate
unknown identifiers before a `:` as `TT_SelectorName` for Objective-C
declaration lines.

Test Plan: New tests included. Confirmed tests failed before change and
  passed after change. Ran tests with:
  % make -j16 FormatTests && ./tools/clang/unittests/Format/FormatTests

Reviewers: djasper, krasimir, jolesiak

Reviewed By: krasimir

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D48679

llvm-svn: 335983