Disable forceful setting of '-j1', and allow setting WORLDJOBS and KERNJOBS in the config.  This also allows setting the configurations FREEBSD_BUILDWORLD_{,EXTRA}_ARGS and FREEBSD_BUILDKERNEL_{,EXTRA}_ARGS to include '-jN', which is passed through to the world/kernel builds.
Disable forceful setting of '-j1', and allow setting WORLDJOBS
and KERNJOBS in the config.  This also allows setting the configurations
FREEBSD_BUILDWORLD_{,EXTRA}_ARGS and FREEBSD_BUILDKERNEL_{,EXTRA}_ARGS
to include '-jN', which is passed through to the world/kernel builds.

Tested against head@r261419 with '-j10' for world, and '-j6' for kernel,
without any ill side effects.

Sponsored by:	The FreeBSD Foundation

wheelcomplex/crochet-freebsd,wheelcomplex/crochet-freebsd,HardenedBSD/crochet,brd/crochet,wheelcomplex/crochet-freebsd,HardenedBSD/crochet,MattDooner/crochet-freebsd,rm4rty/crochet-freebsd,dankm/crochet-freebsd,teverett/crochet-freebsd,brd/crochet,freebsd/crochet,teverett/crochet-freebsd,brd/crochet,dankm/crochet-freebsd,MattDooner/crochet-freebsd,rm4rty/crochet-freebsd,freebsd/crochet