Reimplement cmp operators for ARM NEON
Reimplement cmp operators for ARM NEON

Our current implementation is broken because it hasn't really been
tested.

This is a naive implementation that checks every single lane for the
expected result of the ARM NEON intrinsics for comparison, as documented
here:

  http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0472k/chr1360928367684.html

Fixes: #97
Fixes: #147
Fixes: #148

ebassi/graphene,ebassi/graphene