Broken compilation on ARM/PowerPC

[pablodelara]

Due to new interface for ec_init_tables for x86, now ec_init_tables does not have a single implementation (base), so it needs to be defined and call ec_init_tables_base function, for aarch64 and PowerPC

Current build issues:
erasure_code/erasure_code_test.c:282: undefined reference to ec_init_tables' /usr/bin/ld: /root/isa-l/erasure_code/erasure_code_test.c:308: undefined reference to ec_init_tables'
/usr/bin/ld: /root/isa-l/erasure_code/erasure_code_test.c:350: undefined reference to ec_init_tables' /usr/bin/ld: /root/isa-l/erasure_code/erasure_code_test.c:376: undefined reference to ec_init_tables'
/usr/bin/ld: /root/isa-l/erasure_code/erasure_code_test.c:421: undefined reference to `ec_init_tables'

PR #259 fixes this issue.

[pablodelara]

Now that #259 is merged, this should be fixed. Feel free to reopen it otherwise.