Dropped old show(1) and renamed mhshow(1) to show(1).

Dropped old show(1) and renamed mhshow(1) to show(1).
If you do want to display non-MIME messages the old way, you can use:
	mhl `mhpath ...`
The choice of renaming was hard to decide because I will introduce confusion
and breaks the interface (mmh broke it already!). I though renamed, because
the new situation is what we actually want: One program to display messages
in a sane way. We used to type `show' and silently got `mhshow' when it
contained non-trivial MIME content. That was a workaround and clearly not
straight-forward. The improve the situation show(1) needed to be dropped.
Because users don't want to type `mhshow', I decided to renamed it to `show'.
Hope I won't introduce too many inconveniences with this decision.