xpkgwedge once, before any other packages have been installed, and
never to delete it. This change finds the prefix of the installed
pre-req package using pkg_info(1), and allows packages to be found in
${X11BASE} and ${LOCALBASE}, not just ${X11PREFIX} - from mail from
Dave Sainty <dave@dtsp.co.nz>, munged slightly by myself.
in preference to X11BASE when trying to find the installed location of
X11 libraries, programs and headers (which will change if xpkgwedge is
installed).
[X11BASE reflects the location of the X11 libs, headers and programs.
X11PREFIX reflects the installed location of X11 packages.]
