removing error from USE_X11 without xorg

[coypu%sdf.org@localhost]

for how pkgsrc hides lookup paths, we need USE_X11 to make xorg paths
visible. we've added a case to make this error if xorg is not installed
at all, but this reached basic packages.

this is familiar in the case of trying to build python w/o xorg. it
errors and asks you to adjust your pkg options.

mostly a question: is shielding users who think pkgsrc should build
xorg for them without setting X11_TYPE=modular more important than
annoying non-graphical users?

since it got to python27, I would say no.

ok to commit?

Index: bsd.pkg.mk
===================================================================
RCS file: /cvsroot/pkgsrc/mk/bsd.pkg.mk,v
retrieving revision 1.2031
diff -u -r1.2031 bsd.pkg.mk
--- bsd.pkg.mk	28 May 2018 20:37:47 -0000	1.2031
+++ bsd.pkg.mk	16 Jul 2018 09:08:43 -0000
@@ -477,9 +477,6 @@
 PKG_SKIP_REASON+= "${PKGNAME} is restricted:" \
 	 "    "${RESTRICTED:Q}
 .  endif
-.  if defined(USE_X11) && (${X11_TYPE} == "native") && !exists(${X11BASE})
-PKG_FAIL_REASON+= "${PKGNAME} uses X11, but ${X11BASE} not found"
-.  endif
 .  if defined(BROKEN)
 PKG_FAIL_REASON+= "${PKGNAME} is marked as broken:" ${BROKEN:Q}
 .  endif