package/upmpdcli: Add patch to fix OPEN_MAX build error

When building upmpdcli with certain toolchains using the compiler flag
-std=c++0x let gcc not define "linux" or "__linux", but "__linux__". Therefore,
the Linux-specific code in closefrom.cpp is not used and the build fails.

Fixes:
http://autobuild.buildroot.net/results/d66/d660a9409552b3e1ad9e3ed716386fd0a67fd8db
http://autobuild.buildroot.net/results/f19/f19e843cdcc968a72919ca3792a90dd40552bd59
http://autobuild.buildroot.net/results/a77/a776001dae51c4dae1f25b3a9bf9a9fe2ca69003
http://autobuild.buildroot.net/results/3e7/3e7590566ed3cc7a1dd412fb66b7b987e847aa25

and many more.

Pull request is open on github [1].

[1]
https://github.com/medoc92/upmpdcli/pull/15



Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>