matchbox-lib: apply upstream based patch to include a missing header

The upstream patch can't be applied as-is because the source code of
the file which is patched has changed. A version bump to the latest
release doesn't fix the problem because the upstream patch was applied
after the resease.

Upstream patch:
   http://git.yoctoproject.org/cgit/cgit.cgi/libmatchbox/commit/?id=9315bcce1f01e7d6c00161442d61d3c676794d9d

Fixes:
   http://autobuild.buildroot.net/results/e4d/e4d510ab6ba69f95401e3120ab90ccdff22deb91/



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>