* config/os/gnu-linux/bits/os_defines.h: Include <features.h>.
If not glibc 2.1 or higher, include <gnu/types.h> and define
__off64_t as __loff_t and #define __THROW as empty.
* libio/libio.h [__P]: Move __THROW and __PMT into their own
ifndef:s.
From-SVN: r37695