Provide -fcf-protection=branch,return.

Provide -fcf-protection=branch,return.

Use EnumSet instead of EnumBitSet since CF_FULL is not power of 2.
It is a bit tricky for sets classification, cf_branch and cf_return
should be in different sets, but they both "conflicts" cf_full,
cf_none. And current EnumSet don't handle this well.

So in the current implementation, only cf_full,cf_none are exclusive
to each other, but they can be combined with any cf_branch, cf_return,
cf_check. It's not perfect, but still an improvement than original
one.

gcc/ChangeLog:

	PR target/89701
	* common.opt: (fcf-protection=): Add EnumSet attribute to
	support combination of params.

gcc/testsuite/ChangeLog:

	* c-c++-common/fcf-protection-10.c: New test.
	* c-c++-common/fcf-protection-11.c: New test.
	* c-c++-common/fcf-protection-12.c: New test.
	* c-c++-common/fcf-protection-8.c: New test.
	* c-c++-common/fcf-protection-9.c: New test.
	* gcc.target/i386/pr89701-1.c: New test.
	* gcc.target/i386/pr89701-2.c: New test.
	* gcc.target/i386/pr89701-3.c: New test.