Add support for loading of yajl.dll on Windows

Yajl built with default build settings yields yajl.dll, so make an
attempt to load this.

At the moment, the existing load structure has simply been duplicated
to achieve this. This could be refactored into something cleaner.

Author: sproberts92

yajl/yajl_common.py

@@ -38,6 +38,13 @@ def load_yajl():
             return cdll.LoadLibrary(yajlso)
         except OSError:
             pass
+
+    yajlso = 'yajl.dll'
+    try:
+        return cdll.LoadLibrary(yajlso)
+    except OSError:
+        pass
+
     raise OSError('Yajl shared object cannot be found. '
         'Please install Yajl and confirm it is on your shared lib path.')