DECLARE_NO_INITMOD fixes

Not sure how it was working before.
Probably because we used all initmods in the tests.
Fix infinite recursion in certain simplifications

Simplifying EQ uses bounds inference to disprove equality, but bounds
inference sometimes uses simplify EQ to prove absence of overflow.
Merge branch 'master' of github.com:halide/Halide
Restored missing simplify call
Arm inverse sqrt was using the wrong instructions.
Relax accuracy requirement for inverse sqrt on arm
Implemented recycling of stack allocations.
Added explicit bounds on FFTs.
Merge branch 'master' of https://github.com/halide/Halide
Merge branch 'master' into recycle_stack
Re-enabled computing column FFTs on strips (instead of root).