Restructure the following packages:

databases/sqsh
databases/sqsh-motif
databases/sqsh-x11

The latter two are now just databases/sqsh built with a specific set of
options.  Changes include:

+ Add options.mk that supports three options:

sqsh-motif Motif GUI
sqsh-xaw Athena GUI
sybase-openclient Use real Sybase

  Note that USE_SYBASE_OPENCLIENT is a legacy variable for the new
  global "sybase-openclient" option.

+ Remove Makefile.common and move all logic into sqsh/Makefile and
  sqsh/options.mk.

+ Remove section in patch-aa that tried to deal with termcap/curses
  issues for readline.  That is now automatically taken care of in
  pkgsrc through termcap.buildlink3.mk, which is included here
  indirectly by readline/buildlink3.mk.

+ Add full DESTDIR support.

+ Bump the PKGREVISION for sqsh, sqsh-motif and sqsh-x11 to 5.  All
  three packages now track and use the same PKGREVISION number.

(jlam)