mhbuild: Removed the -ebcdicsafe switch.

mhbuild: Removed the -ebcdicsafe switch.
It only influenced MIME messages, where quoted-printable encoding encoded
some punctuation chars (e.g. $) as well. I guess this is not much of a
problem anymore today. The switch was deactivated by default and didn't even
appear in the 1991's version of Jerry Peek's MH book. In the 1999's version
there is a parenthesed note about the switch, not more. I guess we won't
miss it.