Revert "Remove harmful attempts to be helpful in pthread_mutex functions."

This reverts commit 432cf5170fbdbd21a28cf5295c2b1d3e78c744de.
Revert "ARM: Change dmb domain for bionic_atomic_barrier()"

This reverts commit 0aaffdaa1b7fcd469e835dc523f96a641dc4610e.
Revert "Clean up the pthread-only atomic stuff a little."

This reverts commit 4594a50eb74cdaa4c595e520926a73b92279c62d.
Revert "Clean up some ARMv4/ARMv5 cruft."

This reverts commit 6cd7ab30bb4e2361168917d46dc460c7be2d9972.