This partially reverts commit f00c6c5b13.
On Ctrl+C, we need to execute cleanup code. For instance, if recording
is enabled, we need to write MP4 file trailer on exit.
Custom SDL signal handlers were disabled because it leaded to process
hanging on Ctrl+C during network calls on initialization, but now it
seems to work correctly, the network calls return immediately on signal.
d0e090e1f9