references of the pkglint package.
_PKGSRCDIR is an internal definition in bsd.pkg.mk, and a few packages
which would like to refer to other packages in the build tree. It should
not be set by users, but neither should it stop a user from building a
package if it is defined, so make it obvious that this is the case.
first component is now a package name+version/pattern, no more
executable/patchname/whatnot.
While there, introduce BUILD_USES_MSGFMT as shorthand to pull in
devel/gettext unless /usr/bin/msgfmt exists (i.e. on post-1.5 -current).
Patch by Alistair Crooks <agc@netbsd.org>
