Added core.sys.posix.sys.resource

This is a translation of the sys/resource.h header for Linux, Mac OS X,
FreeBSD and Solaris.
fix __USE_FILE_OFFSET64 usage
add missing rusage struct field for linux

- these are non-XSI fields but are needed for the
  the size of the struct, e.g. getrusage(int, rusage*)

Conflicts:
	src/core/sys/posix/sys/resource.d
FreeBSD: get/setpriority take int rather than id_t
Merge pull request #445 from kyllingstad/sysresource

Added core.sys.posix.sys.resource