PolyLib backend: clean up simplification of constraints in cloog_equal_add
PolyLib backend: clean up simplification of constraints in cloog_equal_add

cloog_equal_add gets called when the lower and upper bound of a loop
are equal.  When the bounds are constants, then they are rounded up/down
before checking equality.  cloog_equal_add therefore needs to perform
the same rounding.

The original implementation was fairly complicated and apparently
had a bug (as witnessed by the walters test case that will be added later).
The new implementation does not have this bug.

Problem reported by Johan Walters <jwalters@compaandesign.com>

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

heysion/cloog-clone,heysion/cloog-clone,epowers/cloog,heysion/cloog-clone,UBERTC/cloog,VanirLLVM/toolchain_cloog,SaberMod/cloog-current,Distrotech/cloog,cfx-next/toolchain_cloog-upstream,UBERTC/cloog,Syllo/cloog,periscop/cloog,epowers/cloog,UBERTC/cloog,VanirLLVM/toolchain_cloog,periscop/cloog,cfx-next/toolchain_cloog-upstream,epowers/cloog,cfx-next/toolchain_cloog-upstream,SaberMod/cloog-current,Distrotech/cloog,evaautomation/cloog,evaautomation/cloog,VanirLLVM/toolchain_cloog,Syllo/cloog,Distrotech/cloog