forw(1) does always MIMEify now.

Removed the -(no)mime, -(no)format, -filter switches. If you like to forward
messages in non-MIME format, then manually read in the output of:
	mhl -forwall -form mhl.forward `mhpath MSGS...`
Digest do get MIMEified too. To send non-MIME digests use:
	mhl -forwall -from mhl.digest -digest X -volume Y -issue Z `mhpath ...`