Port to FreeBSD

Sponsored-by: EMC / Isilon Storage Division
Fix the mkdirat prototype

Sponsored-by: EMC / Isilon Storage Division
Remove some unused headers, shuffle around others, and fill in string.h for strerror

Sponsored-by: EMC / Isilon Storage Division
Port to FreeBSD

Sponsored-by: EMC / Isilon Storage Division
Fully support 64-bit capable platforms on FreeBSD

Sponsored-by: EMC / Isilon Storage Division