Restore __srget and __swbuf for LP32.

Anthony King <anthonydking@slimroms.net> reports that for Grouper the
Nvidia GL blobs need access to __swbuf. This is because the old <stdio.h>
had inline getc and putc implementations that directly referred to these
symbols.

Change-Id: I11a7b5550018ecc93d8f195c99857759669b2906