libstdc++: Rename __atomic_compare to __atomic_eq

libstdc++: Rename __atomic_compare to __atomic_eq

This is an equality comparison rather than a three-way comparison like
memcmp and <=>, so name it more precisely.

libstdc++-v3/ChangeLog:

	* include/bits/atomic_timed_wait.h
	(__atomic_wait_address_until_v): Replace __atomic_compare with
	__atomic_eq.
	(__atomic_wait_address_for_v): Likewise.
	* include/bits/atomic_wait.h (__atomic_compare): Rename to
	__atomic_eq.
	(__atomic_wait_address_v): Replace __atomic_compare with
	__atomic_eq.