Add `curses` prefix to global variables names in `_cursesmodule.c`

[picnixz]

Feature or enhancement

Proposal:

Some global variables are modified in _cursesmodule.c by other functions and their names can be confused with a local variable name. I wanted to use uppercase names but Victor argued that this should be reserved for C macros (#123910 (comment)) and suggested keeping prefixed lowercase names.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

[picnixz]

Closing in favor of #123961 instead of having many issues.