package/musepack: fix musl build

This commit adds two patches needed to fix musl related build issues
in musepack: a missing <sys/select.h> inclusion, and an inclusion of
<fpu_control.h> that should be made conditional on __GLIBC__.

Fixes:

  http://autobuild.buildroot.net/results/6eb/6ebc9cbee3fc48f4f5b658d11b040ad62fb6607f/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
[Thomas: split the patch in two patches, add proper patch
description.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>