Updated to Pike 0.6 level, except for the stack_swap() calls.

Rev: src/modules/Gmp/Makefile.in:1.8
Rev: src/modules/Gmp/configure.in:1.2
Rev: src/modules/Gmp/gmp_machine.h.in:1.2
Rev: src/modules/Gmp/mpz_glue.c:1.27
Rev: src/modules/Gmp/my_gmp.h:1.3
Rev: src/modules/Gmp/next_prime.c:1.6
Rev: src/modules/Gmp/prime_table.c:1.3
Rev: src/modules/Gmp/testsuite.in:1.8