Log Message:
* Add GUILE14, GUILE14_CONFIG, and GUILE14_SNARF that may be used by packages
  to invoke the guile, guile-config, and guile-snarf binaries from the
  guile14 installation.

* GUILE14_PREFIX, the result of "pkg_info -p guile14".

* GUILE14_SUBDIR, the subdir relative to ${LOCALBASE} where guile14 is
  installed.

* Replace for ${BUILDLINK_DIR}/bin/guile in config files when unbuildinking.

* Symlink the guile14 libtool archives into ${BUILDLINK_DIR}/lib to suppress
  find the libtool archives from a guile package installed into ${LOCALBASE}.
  We can no longer include both guile/buildlink2.mk and guile14/buildlink2.mk
  as a result of this change.