reference leak in module init

[maxbachmann]

Inside module init strings are created:

#ifdef LEV_PYTHON3
    opcode_names[i].pystring
      = PyUnicode_InternFromString(opcode_names[i].cstring);
#else
    opcode_names[i].pystring
      = PyString_InternFromString(opcode_names[i].cstring);
#endif
    opcode_names[i].len = strlen(opcode_names[i].cstring);

These strings are not NULL checked, so if allocation fails strlen causes a segmentation fault.
In addition the strings are not deallocated since the reference count is never cleared.

[maxbachmann]

Fixed in #10