SIGPIPE handling

I've had requests from several users now to change the default SIGPIPE handling to "stop = false, notify = false". The argument is that most of the time these signals are generally ignored and folks directly handle the read and write errors. So having lldb stop by default for SIGPIPE is just annoying. And if SIGPIPE debugging is interesting for some project, it is easy to turn this back on. TTTT I just copied the gdb defaults as they were 10 years or so ago, there wasn't a better motivation for the way it is in lldb now.

The change is easy, but I wanted to make sure nobody has a counter-argument for keeping the current default - which is stop = yes, notify = yes, suppress = no. I'm proposing to change that to stop = no, notify = no, suppress = no.