configure_cross for host fails because of mp_limb_t is 32 bits

[dschuermann]

./configure_cross host fails with
"configure: error: Oops, mp_limb_t is 32 bits, but the assembler code
in this configuration expects 64 bits."

Fixed it by adding "ABI=32 " to the config_opts for the host in configure_cross

[ageneau]

I think this is because you didn't compile and install GMP first (using configure_cross_gmp) so ECL will compile it as part of the ECL build.