* sigproc.h (sigframe::set): Eliminate second argument. Default bp to current

* sigproc.h (sigframe::set): Eliminate second argument.  Default bp to current
frame pointer rather than using this within the function, which is unstable
when this method is not inlined.
* net.cc: Eliminate use of second argument to sigframe.set throughout.
* select.cc (cygwin_select): Ditto.
* sigproc.cc (sig_send): Ditto.