Gibbing now occurs in whatever the mob happens to be in, instead of fetching the turf.
Larvae who chestburst while their host is swallowed are now properly added to stomach_contents, so they can be regurgitated.  As are the gibs from the gibbing.
Tidied up the loop in alien_powers.dm
Merge pull request #2455 from Rolan7/Issue297_Gib_Fix

Issue 297 Gibbing in pipes fix