abort and onAbort
moved `wind` and `isTruthy` to more appropriate places
Merge branch 'nocontrol' into control

Conflicts:
	Language/SFCC/Interpreter.hs
newPrompt primitive
added show for reference cells
Merge branch 'nocontrol' into control

Conflicts:
	Language/SFCC/Support.hs
new abort strategy; fixed bug where environments are not restored when executing onAbort handlers
handler form
tested out defining subroutines (functions that can early-exit with a value)
onWind form
capture/restore forms (incl. testing); lazy closures wrap extra args in implicit begin with last expected argument
testing onWind: success
remane div/mode -> quo/rem; protect against divide by zero
Merge branch 'nocontrol' into control
using lazy closures induces implicit begin
Merge branch 'nocontrol' into control
found a bug regarding environment management in the precense of control effects
fixed accidental environment updates, but found a bug in on-wind.amon
heh, it was a durp bug