Merge pull request #49 from Turakar/turtle-dev

Fixed turtle.detectUp and turtle.detectDown
The div functions should free their own 4

Instead of an unexplained free(5) in the calling sites.
Long division / modulo

Not functioning yet
emitComment

Emit comments on the next instruction
Multiple comments on one emit
LOTS more comments in the emitter
Nil check at bigint api entry points
Should free 5, not 4
Fixed #50

Among other potential arithmetic issues
Comments on emitInsert
Merge remote-tracking branch 'upstream/master'