MINOR: contrib: dummy wurfl library

MINOR: contrib: dummy wurfl library

This is dummy version of the Scientiamobile WURFL C API that can be used
to successfully build/run haproxy compiled with USE_WURFL=1.
It is marked as version 1.11.2.100 to distinguish it from any real version
of the lib. It has no external dependencies so it should work out of the
box by building it like this :

   $ make -C contrib/wurfl

In order to use it, simply reference this directory as the WURFL include
and library paths :

   $ make TARGET=<target> USE_WURFL=1 WURFL_INC=$PWD/contrib/wurfl WURFL_LIB=$PWD/contrib/wurfl