Replaced outdated macros _PyUnicode_AsString and _PyUnicode_AsStringAndSize

with PyUnicode_AsUTF8 and PyUnicode_AsUTF8AndSize.

diff --cc Modules/_datetimemodule.c
Simple merge

diff --cc Modules/posixmodule.c
Simple merge

diff --cc Modules/socketmodule.c
Simple merge

diff --cc Python/ceval.c
Simple merge

diff --cc Python/sysmodule.c
Simple merge