PORT: Bug#64: Define _XOPEN_SOURCE if __GNU__ is defined.
PORT: Bug#64: Define _XOPEN_SOURCE if __GNU__ is defined.

edechter/swipl-devel,jn7163/swipl-devel,mndrix/swipl-devel,edechter/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,jn7163/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,jn7163/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,jn7163/swipl-devel,edechter/swipl-devel,jn7163/swipl-devel,mndrix/swipl-devel