Fix: ws_transaction_new() comparsion
Fix: deserializer_state(_new())

This patch fixes the deserializer_state type as well as the
deserializer_state_new() function. We don't need to cache the allocation
type here. It also adds an initialization for the bracket counting and
the ID (zero is an invalid ID now).
Fix: ws_transaction_push_statement()

This patch fixes the ws_transaction_push_statement() function by
doing a (almost) complete rewrite.

The code was tested in another branch.
Merge pull request #299 from matthiasbeyer/fix-for_json_deserializer

Fixes/Preparation for json deserializer
Add deserializer callback interface
Add deserializer callback source file (stubs) and CMakeLists.txt entry
Add implementation for NULL callback
Add implementation for boolean callback
Add implementation for integer callback
Add implementation for string callback
Add implementation for start_map callback
Add implementation of map_key callback
Add implementation of end_map callback
Add implementation of start_array callback
Add implementation of end_array callback
Set callback table
Add key for stack position argument type
Add state for stack position argument type state
Initial json deserializer testing setup
Add test for init/deinit deserializer