Log message:
Remove mk/find-prefix.mk usage from the x11 category.

The find-prefix infrastructure was required in a pkgviews world where
packages installed from pkgsrc could have different installation
prefixes, and this was a way for a dependency prefix to be determined.

Now that pkgviews has been removed there is no longer any need for the
overhead of this infrastructure.  Instead we use BUILDLINK_PREFIX.pkg
for dependencies pulled in via buildlink, or LOCALBASE/PREFIX where the
dependency is coming from pkgsrc.

Provides a reasonable performance win due to the reduction of `pkg_info
-qp` calls, some of which were redundant anyway as they were duplicating
the same information provided by BUILDLINK_PREFIX.pkg.

Log message:
Add SHA512 digests for distfiles for x11 category

Problems found locating distfiles:
        Package modular-xorg-server: missing distfile xorg-server-1.17.4.tar.bz2
        Package py-qt4: missing distfile PyQt-mac-gpl-4.11.1.tar.gz
        Package xservers: missing distfile xservers-3.3.6.5.tar.bz2
        Package xview-clients: missing distfile xview3.2p1-X11R6.tar.gz
        Package xview-lib: missing distfile xview3.2p1-X11R6.tar.gz

Otherwise, existing SHA1 digests verified and found to be the same on
the machine holding the existing distfiles (morden).  All existing
SHA1 digests retained for now as an audit trail.

Log message:
Remove pkgviews: don't set PKG_INSTALLATION_TYPES in Makefiles.

Log message:
Provide upper limit for the Tk dependency. No revbump as the only user
wouldn't build against 8.6 anyway.

Log message:
Restore tk-8.5.15 package as lang/tk85 with bump PKGREVISION since
x11/ruby-tk package needs tcl/tk 8.5 and it dosen't support tcl/tk 8.6
and later.