Be more relaxed if something is before PGP Marker

* src/mapihelp.cpp (get_msgcls_from_pgp_lines): Remove abort
statement for text before message.

This might cause problems in case somone does something
like:

Hey here is your password encrypted:
-----BEGIN PGP MESSAGE-----

But meh. It's more robutst this way in case we have an
MTA that modifies the body.