Apparently, it does not fully conforms to POSIX as README claims - AFAIK, that "_POSIX_X_SOURCE" feature test macro should be defined with positive integer valu

Apparently, it does not fully conforms to POSIX as README claims - AFAIK, that "_POSIX_X_SOURCE" feature test macro should be defined with positive integer value per POSIX standard, not empty as defined in bestline.c