Test handling of additional brk instruction patterns

Test handling of additional brk instruction patterns

New in v5:

- Use gdb_test_name for gdb_test_multiple.
- Use gdb_assert.
- Verify count matches the expected sigtraps exactly.

New in v4:

- Fix formatting nit in gdb/testsuite/gdb.arch/aarch64-brk-patterns.c.

New in v3:

- Minor formatting and code cleanups.
- Added count check to validate number of brk SIGTRAP's.
- Moved count to SIGTRAP check conditional block.

This test exercises the previous patch's code and makes sure GDB can
properly get a SIGTRAP from various brk instruction patterns.

GDB needs to be able to see the program exiting normally. If GDB doesn't
support the additional brk instructions, we will see timeouts.

We bail out with the first timeout since we won't be able to step through
the program breakpoint anyway, so it is no use carrying on.

gdb/testsuite/ChangeLog:

2020-01-29  Luis Machado  <luis.machado@linaro.org>

	* gdb.arch/aarch64-brk-patterns.c: New source file.
	* gdb.arch/aarch64-brk-patterns.exp: New test.