This adds to the ObjC language guesser a few more common macros used
in ObjC headers. These can help distinguish ObjC headers which
otherwise lack ObjC types from C++ headers.
Contributed by danblakemore.
Tested: New tests included. Ran unit tests with:
```
% cmake -S llvm -B build -G Ninja && \
ninja -C build FormatTests && \
./build/tools/clang/unittests/Format/FormatTests --gtest_filter="*FormatTestObjC*"
(snip)
[----------] 24 tests from FormatTestObjC (265 ms total)
[----------] Global test environment tear-down
[==========] 26 tests from 2 test suites ran. (270 ms total)
[ PASSED ] 26 tests.
```
Reviewed By: MyDeveloperDay
Differential Revision: https://reviews.llvm.org/D151578
85670ac868