About one month worth of bsd.port.mk improvements.

About one month worth of bsd.port.mk improvements.

(1) Allow multiple checksums of same file.
Submitted by:	hoek

(2) Add "deinstall" target as an alias to "pkg_delete $(make package-name)"
    (well, something like that, see diff for details).

(3) Add new port variable USE_AUTOCONF.   It appends BUILD_DEPENDS to
    devel/autoconf and runs autoconf before configure.
Submitted by:	ohashi@mickey.ai.kyutech.ac.jp (Takeshi Ohashi)

(4) Clarify USE_X11 and USE_IMAKE usage.

(5) Add new user-overridable variable MASTER_SITE_KDE.
Submitted by:	vanilla

(6) Add support for "Latest" package links.
Idea by:	Terry Lambert

(7) Try to catch obsolete tcl/tk installations that could cause problems.
Annoyed by various bogus commits by:	you-know-who