* Fixes issue #51
* Adds a specific error message for when you try to pop an empty list.
* Releases some memory if the list has shurnk a lot.

mpconfig.h will automatically pull mpconfigport.h.

This is just max value of current_bytes_allocated seen.

Unlike total_bytes_allocated, this tracks m_free()'s too.

import works for simple cases.  Still work to do on finding the right
script, and setting globals/locals correctly when running an imported
function.

Generator objects now allocate the object and the state in one malloc.
This improvement fixes Issue #38.

This is based on the fact that qstr so far behaves more like byte string
than like Unicode string (for example, "012"[0] returns 48 (int)).

This fixes Issue #29, and means the core is no longer dependent on
string functions, except strlen.