When recompiling an already loaded file, the macroexpansion-time check
for FBOUND prevents the definition to be compiled, and when the resulting
fasl is loaded into a fresh image, the definition will be missing.
Move the fbound check into the expansion itself.

James M. Lawrence authored Jun 29, 2012 and Stelian Ionescu committed Jul 29, 2012

If release-lock fails then do not call acquire-lock.

Bug reported by Mizumaru Kiyoshi

Thanks to Kilian Sprotte for reporting this.