Can't interrupt process without controlling terminal on Solaris (PR gdb/8527)

If gdb attaches to a process that either has no controlling terminal,
or the controlling terminal differs from the one gdb is running under,
break/^C doesn't interrupt the debugged process on Solaris.

Fixed as follows, analogous to what all all other targets do.  Patch from
the PR, recently re-submitted by Brian Vandenberg.

Tested on amd64-pc-solaris2.11, sparcv9-sun-solaris2.11, and
x86_64-pc-linux-gnu.

2019-02-28  Brian Vandenberg  <phantall@gmail.com>
	    Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gdb:
	PR gdb/8527
	* procfs.c (proc_wait_for_stop): Wrap write of PCWSTOP in
	set_sigint_trap, clear_sigint_trap.

	gdb/testsuite:
	PR gdb/8527
	* gdb.base/interrupt-daemon-attach.c,
	gdb.base/interrupt-daemon-attach.exp: New test.