apply-distribution-patches and apply-pkgsrc-patches. Rewrite the
latter code to be more "whitespace-friendly" and to not need to invoke
${AWK} as many times. Drop support for PKGSRC_SHOW_PATCH_ERRORMSG
and simply always show the error message.
separate file pkgsrc/mk/bsd.pkg.patch.mk. Also, include this file
ahead of the inclusion of bsd.tools.mk so that tools required to
patch are created by the tools framework.