Fix up optional inclusion of backup mp_get_memory_functions implementation
Fix up optional inclusion of backup mp_get_memory_functions implementation

Commit fb17acca9c26d3299c3eece032584345b28d0af0 (Add backup
mp_get_memory_functions implementation for use with old gmps)
introduced a NEED_GET_MEMORY_FUNCTIONS condition, but only defined
it if gmp was used, breaking non-gmp builds.

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