[rcore_desktop] Fix 3693 initial window geometry (#3950)

* Rework window placement and dimensions for multi-monitor setups;

- fullscreen apps use primary monitor, exclusively
- non-fullscreen apps come in two variants:
a) pre-determined window size by user
b) use-active-monitor dimensions by user specifying 0x0
Either way, the window shall be centred at the monitor where it was created

This may have been the original intent, yet the primary monitor was used also for the second case, regardless where the window opened.

* Clean up code, handle error, fix integer-overflow for centering windowed fullscreen

0 files changed, 0 insertions, 0 deletions