quota: fix build on musl

This commit adds 3 patches to the quota package, that allows to build
it with musl. One patch was borrowed from OpenEmbedded, the other two
patches are really trivial.

Fixes:

  http://autobuild.buildroot.net/results/6f0ff905251d12e198654b8ffe0ea5c15186371e/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>