Changed the new "plussed_user" option to mts.conf's "masquerade:" to

Changed the new "plussed_user" option to mts.conf's "masquerade:" to
"username_extension" after getting feedback from qmail users, who use '-' as a
separator rather than '+'.  Removed checking of $USERPLUS variable.  Now check
$USERNAME_EXTENSION, which needs to include the appropriate separator for your
MTA ('-', '+', or whatever) as its first character.