#282 "default" option for the metapost terminal

[Mojca Miklavec]

This tiny patch adds the option "default" to metapost
terminal (some irrelevant changes in spaces/tabs were
made on purpose).

It would be great if the terminal could be also called
"set term metapost", not only "mp". Are there any
strong objections against that?

[Mojca Miklavec]

adds "default" terminal option