jsoncpp: fix build for non C++11 toolchains

jsoncpp: fix build for non C++11 toolchains

Add a patch removing reference to std::snprintf that is only in C++11.

Fixes:
http://autobuild.buildroot.net/results/b39/b390beeb9a6fea12f1a4d9f2ff9a8a483628cad2/
http://autobuild.buildroot.net/results/d18/d18b3e116b680a3897fbea296938e900a1e5e80a/
http://autobuild.buildroot.net/results/1b2/1b20a2f81dd2b409785930705222bc03576c4907/

and many more.

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