Disable forcing and collapsibility (dirty hack).
Fix erasure from data ctors.
Erase unused case-branches.

Conflicts:
	src/Idris/Erasure.hs
Fix reg005.
More small fixes.
Handle Nat projections correctly.
Fix single-arg-ness of ProjCase.
Fix double type signature for pi.
Remove the last occurrence of "force".
Remove the Lazy flag entirely.
Remove prim_io_bind and prim_io_return from run__IO.
Improve comments.
Improve printing of foreign calls.
Unified printing of special LTerms.
Add "detaggable" as an argument to OptInfo.
Add detaggability recognition.
Compile data ctors with real arity.
Include erasure in data constructors.
Fix optimisation IBC stuff.
Add newtype-case elimination.