+ Pass down the correct values for TERMCAP (the options to link to
  the library containing termcap functions) and MISC_TERMINFO_DIRS
  (the location of the terminfo database).  Patch the configure script
  to use these values instead of using its own broken logic to determine
  the same information.

+ Include termlib.buildlink3.mk to determine the right terminal library
  to use.

The above two changes should fix PR pkg/30725.

+ Move the HTML documentation into ${PREFIX}/share/doc/slang.

Bump the PKGREVISION to 6.

(jlam)