uclibc: add kconfig option and make stuff for installing the uClibc test suite

This patch adds the possibility to install the uClibc test suite to the target
file system. This is useful if you need to debug or test your uClibc.

The option is defaulted to no, and is not needed for a normal running Linux
system. The test suite is installed to /root/uClibc

Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>