FFplay ignores stdin

[btdmaster]

FFplay ignores stdin; only the window spawned can be used to control output.

Steps to reproduce:
ffplay arbitraryvideofile.mkv # or any other file
# Go back to spawning terminal emulator. Type in q to quit.

Expected result:
FFplay would quit.

Actual result:
Terminal emulator receives stdin, FFplay does nothing.

The same applies for all the other hotkeys. This is worse with -nodisp, as the lack of a graphical display means that, effectively, there is no way to modify the output like change volume. Because of this it is important that FFplay takes into account input from stdin.