Make ^C work in the DRM backend

[matthijskooijman]

When running the DRM platform, currently the process cannot be terminated using control-C, which is not very convenient for development.

I see this might be intentional, given the comment above the relevant code:

raylib/src/platforms/rcore_drm.c

Lines 1431 to 1433 in 852c513

	// New terminal settings for keyboard: turn off buffering (non-canonical mode), echo and key processing
	// NOTE: ISIG controls if ^C and ^Z generate break signals or not
	keyboardNewSettings.c_lflag &= ~(ICANON | ECHO | ISIG);

(I tried this, removing ISIG from that line makes ^C work)

Is there any reason for this ISIG to be there? The tcsetattr(3) manual says:

ISIG When any of the characters INTR, QUIT, SUSP, or DSUSP are received, generate the corresponding signal.

Seems like this would not be problematic for a typical application?

[raysan5]

@matthijskooijman That code was writen long ago, sincerely, I don't remember at the moment why it was there. If you tested the DRM backend with that change and couldn't find any issue, feel free to send a PR with the update... Maybe it was there to support Copy-Paste functionality on user applications? I don't remember...