Add tablist support and a mandoc-manpage to expand(1)

and mark it as finished in the README.

This is another example showing how broken the GNU coreutils are:

$ echo -e "äää\tüüü\tööö" | gnu-expand -t "5,10,20"
äää    üüü    ööö
$ echo -e "äää\tüüü\tööö" | sbase-expand -t "5,10,20"
äää  üüü  ööö

This is due to the fact that they are still not UTF8-aware and
actually see "ä" as two single characters, expanding the "äää" with
4 spaces to a tab of length 10.
The correct way however is to expand the "äää" with 2 spaces to a
tab of length 5.
One can only imagine how this silently breaks a lot of code around
the world.
WHAT WERE THEY THINKING?

README

@@ -28,7 +28,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =  du              no                              -H, -L, (-x)
 =* echo            yes                             none
 =* env             yes                             none
-#  expand          yes                             none
+#* expand          yes                             none
    expr            yes                             none
 =* false           yes                             none
    fold            yes                             none