Improve launch diagnostic messages, switch off supply
msl_equip() used mission_pln_equip(), which is for automatic defenses,
and therefore silent. Its users launch_as(), launch_missile() and
launch_sat() printed failure diagnostics based on assumptions on what
could go wrong.
Switch to the appropriate function for commands, pln_equip(), and
remove the guesswork. Implement mission 'i' there. When launching
from a foreign base, its owner now gets informed. Unimportant at this
time, as players can't easily deploy missiles in foreign bases.
This change also switches off automatic supply for launch. Consistent
with bomb.