This is a new memory subsystem implementing heap calculations as well as new builtin functions:
* get_memory_usage()
* get_memory_peak_usage()
* get_memory_limit()
It also allows to set an upper memory limit, ensuring that processed script will not be able to allocate more memory from OS.
New subsystem is based on work done in 'memory_limit' branch. Big thanks to devnexen!
This finally fixes#25.
Rafal Kupiec