Log message:
Change all instances of including mk/ghostscript.mk into asking for
the appropriate tool via USE_TOOLS (usually "gs:run"), and remove
ghostscript.mk.  This change removes a rather out-dated file from
pkgsrc and switches packages to use the more compact implementation
of the Ghostcript-handling inside the tools framework.

Log message:
Get rid of USE_PERL5.  The new way to express needing the Perl executable
around at either build-time or at run-time is:

	USE_TOOLS+=	perl		# build-time
	USE_TOOLS+=	perl:run	# run-time

Also remove some places where perl5/buildlink3.mk was being included
by a package Makefile, but all that the package wanted was the Perl
executable.

Log message:
Change the CONFIGURE_ENV to use the variables users are supposed to set,
rather than the autoconf cache variables.

Log message:
Prevent paths to the build directories from being included in the package.
Bump PKGREVISION.

Log message:
Don't use buildlink framework just to do a conditional dependency for a
binary tool.  We can now use the tools framework for this.  Remove the
various nroff/groff buildlink3.mk/builtin.mk files as editors/jove was
their only user in pkgsrc.

Log message:
Remove USE_BUILDLINK3 and NO_BUILDLINK; these are no longer used.

Log message:
Use BUILDLINK_PREFIX.groff, not a local _GROFFPATH.

Log message:
Make build/work on Interix.

How ugly: a hypot(near0, near0) can result in a NaN if round-off error
somehow makes the a^2+b^2 result negative.  Work around it with an
"#ifdef __INTERIX"-only fix.

Log message:
Add RMD160 digests to the SHA1 ones.

Log message:
Temporarily mark as NOT_FOR_PLATFORM=Interix due to endless loop in build.