gamin: fix build with musl

gamin: fix build with musl

musl does not provide the non portable PTHREAD_MUTEX_RECURSIVE_NP. Add a patch
removing the assumption the PTHREAD_MUTEX_RECURSIVE_NP is available when
'linux' is defined.

Upstream had no new release since 2008, so there is no much hope of getting
this fix applied upstream.

Also, fix the pthread dependency comment. gamin code uses pthread directly.

Fixes:
http://autobuild.buildroot.net/results/3a9/3a9328f384fc648ae61316402a84eaffb175881b/
http://autobuild.buildroot.net/results/69d/69d2a93bc97ab0d70c3acb2f9c9f28612ea95871/
http://autobuild.buildroot.net/results/092/092ac7380beb8ce403a1a6fd8e4176e9234413a3/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>