urgent need is when you run sh around a program that intentionally
uses SIGQUIT/SIGINT for asynchronous events, i.e. $EDITOR started from
system(2), like many mailers do. This fixes PR bin/1206 and possibly
bin/4241.
The solution committed has been tested for a large number of possible
cases (see recent discussion on cvs-committers). I completed a make
world, made sure 'make world' is interruptable and used the changed
/bin/sh as a login shell all day, including job control and using
SIGQUIT-catching programs (to write this message :-).
PR: bin/1206
Reviewed by: discussion on cvs-commiters
9dee16dba6