avr32: support uClibc 0.9.33.2

Add a uClibc patch from OpenWRT, and tweak an existing patch to cope with
the lack of a dup3 Linux syscall on avr32. This allow uClibc 0.9.33.2 to be
built for avr32.

[Peter: add upstream url for openwrt patch]
Signed-off-by: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>