Support null terminated string types

[emesare]

https://docs.python.org/3/library/ctypes.html#ctypes.c_char_p
https://docs.python.org/3/library/ctypes.html#ctypes.c_wchar_p

memflow already supports reading null terminated strings. Only on UTF-8 encoded strings, however. We will need our own for c_wchar_p.

[emesare]

Preliminary support added with: e76e46e. Once we move to deduplicate our memory read/write functions, broad support for these null terminated string readers will be added.