Clean up detection of big-endian ARM. In all cases we follow the pattern
arm*eb*. Check we are building for arm and if MACHINE_ARCH follows this
pattern.
Clean up detection of hard-float ABIs. As with big-endian in r272368 we
can check against arm*hf*.
Embellish a comment regarding the reliability of DEBUG_VFS_LOCKS.

Submitted by:	kib