package/yajl: add patch to fix static build issue

mpd's plugin soundcloud requires yajl. In static build context yajl library is
named yajl_s so linking against yajl fails:
  /bin/ld: cannot find -lyajl

Use a pull request patch [1] to let the shared and the static library
have the same name. They will be differentiated by the extension (.so or .a).

Fixes:
http://autobuild.buildroot.net/results/5ac/5acba9b0ed852512fc88e83973a3b5389e6d54be/
http://autobuild.buildroot.net/results/739/73934ad67efa121fedeaa03fdad290aa63f1485e/

[1] https://github.com/lloyd/yajl/pull/174



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