libbe(3): Move build goop back out of cddl/

Some background: in the GSoC project, libbe/Makefile lived in lib/libbe. I
created projects/bectl branch, maintained the above for all of five
minutes before I misread Makefile.inc1 and decided that it couldn't possibly
build outside of cddl/, so I kicked the Makefile out into the cddl/ build
and all was good. The misreading was of the bit where .WAIT is added to
SUBDIR after lib, libexec but prior to building bin and cddl *only during
the install targets*, which is the critical part.

Fast forward- buildworld was still broken in my branch unbeknownst to me
because I didn't nuke my OBJDIR. Combing through Makefile.inc1 eventually
revealed the necessary magic to make sure that libbe's dependencies are
specified well enough, and it becomes clear what needs done to make a
non-cddl/ build work. This is an interesting prospect, because the build
split is kind of annoying to work with.

IGNORE_PRAGMA is added to avoid dropping WARNS by one more. This was
previously pulled in via cddl/Makefile.inc.