send,spost: No more use of -alias, spost reads Aliasfile from the profile.

The profile entry Aliasfile was introduced in MH-6.7 to replace the
-alias switches. Later, the profile entry was enhanced to support multiple
files. Now that spost reads the profile itself, there is no more need
to pass the file with switches. Operating with varying sets of alias
files is now only possible with different profiles, but that should be
a rare setup.