bitbake: user-manual-ref-variables.xml: Added BB* variables to glossary.

bitbake: user-manual-ref-variables.xml: Added BB* variables to glossary.

BB_STRICT_CHECKSUM
BB_WORKERCONTEXT
BB_SIGNATURE_EXCLUDE_FLAGS
BB_HASHBASE_WHITELIST
BB_INVALIDCONF
BB_LOGFMT
BB_RUNFMT
BB_RUNTASK
BB_HASHBASE_WHITELIST
BB_STAMP_POLICY
BB_STAMP_WHITELIST
BB_SCHEDULER
BB_SCHEDULERS
BB_SETSCENE_DEPVALID
BB_SETSCENE_VERIFY_FUNCTION
BB_SIGNATURE_HANDLER
BB_SRCREV_POLICY
BB_VERBOSE_LOGS

(Bitbake rev: f02be6ca79fccc3c7bfbbadeef0c98242f661524)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>