The variable defined in it are now always available after including
bsd.port.pre.mk.
PR: 210666
Submitted by: mat
Exp-run by: antoine
Sponsored by: Absolight
Differential Revision: https://reviews.freebsd.org/D6933
sqlite and firebird handling code has been extracted from bsd.databases.mk
add an entry in bsd.sanity.mk to mark USE_SQLITE and USE_FIREBIRD as deprecated