begin 1.5 development
Enable -Werror & devel mode
use .xz's when we create tarballs
Use xz for the coverity tarballs too
silence some Makefile commands
use a 'v' in the tag name
silence a command that I missed.
Clear main pid before we exit.

Reported and diagnosed by Michael Ellerman.

If we don't do this, the watchdog will spin forever.