Add documentation to ws_value_union_reinit()
Add missing memberof to documentation of ws_value_union_init_from_val()
Merge pull request #452 from neithernut/fix-value-union-documentation

Fix value union documentation
Add error identification

This patch introduces a error member in the deserializer state type to
handle certain parsing errors, such as internal ones (for example
-ENOMEM) and YAJL parsing errors, to be able to tell the plugin what
happened.
Add error identification handling in yajl_null_cb()
Add error identification handling in yajl_boolean_cb()
Add error identification handling in yajl_integer_cb()
Add error identification handling in yajl_string_cb()
Add error identification handling in yajl_map_key_cb()