Do not define _XOPEN_SOURCE for OS X
Do not define _XOPEN_SOURCE for OS X

Resolves failed `make` on OS X.
jinguoli/hiredis,redis/hiredis,thomaslee/hiredis,redis/hiredis,jinguoli/hiredis,redis/hiredis,owent-contrib/hiredis,charsyam/hiredis,owent-contrib/hiredis,jinguoli/hiredis,charsyam/hiredis,thomaslee/hiredis