kFreeBSD needs to be treated as a distinct target from FreeBSD since the underlying system libc is the GNU one. Thus, relying only on __GLIBC__ no longer suffice. - freebsd-glibc new target, key difference is including crypt.h and linking to libdl like linux. - cpu affinity available but the api is still the FreeBSD's. - enabling auxiliary data access only for Linux. Patch based on preliminary work done by @bigon. closes #1555