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
diff --git a/doc/WURFL-device-detection.txt b/doc/WURFL-device-detection.txt
index 0d61db0..41afb17 100644
--- a/doc/WURFL-device-detection.txt
+++ b/doc/WURFL-device-detection.txt
@@ -17,6 +17,16 @@
 
 Optionally WURFL_DEBUG=1 may be set to increase logs verbosity
 
+For HAProxy developers who need to verify that their changes didn't accidently
+break the WURFL code, it is possible to build a dummy library provided in the
+contrib/wurfl directory and to use it as an alternative for the full library.
+This will not provide the full functionalities, it will just allow haproxy to
+start with a wurfl configuration, which generally is enough to validate API
+changes :
+
+    $ make -C contrib/wurfl
+    $ make TARGET=<target> USE_WURFL=1 WURFL_INC=$PWD/contrib/wurfl WURFL_LIB=$PWD/contrib/wurfl
+
 These are the supported WURFL directives (see doc/configuration.txt) :
 - wurfl-data-file <path to WURFL data file>
 - wurfl-information-list [<string>] (list of WURFL capabilities,