Allow userspace-sanitized headers

This makes a couple changes to allow the Android Bionic clean_header.py
script to generate headers for the userspace DDK to use:

* Create macro versions of static inline functions
  base_mem_group_id_set() and base_context_mmu_group_id_set(), since
  the header cleaner passes macros but not functions. The macros don't
  assert on invalid parameter values like the functions do.

* Add parentheses around FOO in "#if defined FOO" since the script doesn't handle
  the parenthesis-free syntax.

Bug: 168545054
Signed-off-by: Jesse Hall <jessehall@google.com>
Change-Id: Ic3c75fd2b5e176341a951a0cbeeb905a35b3276a