gh-153009: Fix compilation of curses on platforms that define the stdscr macro

[picnixz]

• Issue: Build error by using stdscr in curses C extension module #153009

[serhiy-storchaka]

You are fast! LGTM. 👍

[picnixz]

I was fast because I needed that patch for another PR. It was a matter of splitting local work :')

[serhiy-storchaka]

One small naming thought: std_screen reads a bit oddly since the field holds the stdscr window object inside a struct that's already a …ScreenObject — something like stdscr_win or std_win would say what it holds without colliding with the macro. Purely cosmetic, so feel free to keep std_screen if you prefer it.

[picnixz]

I like the stdscr_win