built_in: Add __noreturn marker

This can be used to mark functions which will call exit() by themselves.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
die.h: Add __noreturn attribute to exiting functions

Add the __noreturn attribute to all functions which wont return but call
exit() (or die() respectively) themselves.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
netsniff-ng: Add __noreturn attribute to exiting functions

Add the __noreturn attribute to all functions which wont return but call
die() themselves to exit().

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
trafgen: Add __noreturn attribute to exiting functions

Add the __noreturn attribute to all functions which wont return
but call die() themselves to exit().

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>