Avoid overwhelming expect's buffer

"expect" has a default buffer size of 2000 bytes ("match_max").

If the testsuite programs send large amounts of data to stdout/stderr,
they could overwhelm this buffer.

Avoid this.

gcc/testsuite/ChangeLog.jit:
	* jit.dg/harness.h [MAKE_DEJAGNU_H_THREADSAFE] (note): Redefine
	"note" from dejagnu.h to new function dejagnu_note so that we can
	make "note" be threadsafe.
	(set_options): Don't enable GCC_JIT_BOOL_OPTION_DUMP_SUMMARY,
	since it can generate large amounts of output that could overwhelm
	expect's buffer.
	* jit.dg/test-dot-product.c (verify_code): Use "note" rather than
	"printf", to give DejaGnu more chances to parse this log data,
	rather than overflowing its buffer.
	* jit.dg/test-factorial.c (verify_code): Likewise.
	* jit.dg/test-fibonacci.c (verify_code): Likewise.
	* jit.dg/test-fuzzer.c (main): Likewise.
	* jit.dg/test-nested-loops.c (verify_code): Likewise.
	* jit.dg/test-sum-of-squares.c (verify_code): Likewise.
	* jit.dg/test-threads.c (note): New function, adding thread-safety
	on top of "dejagnu_note", the latter being the implementation
	found in dejagnu.h.
	(run_threaded_test): Use "note" rather than "printf".
Work around a bug in dejagnu.exp's host_execute

dejagnu.exp's host_execute has a bug, which (for me) reliably breaks
the jit testsuite when running "make check" (though not when
running "make check-jit" by itself, and appears to be unpleasantly
timing-related).

See the discussion at:
  http://lists.gnu.org/archive/html/dejagnu/2014-10/msg00000.html

For now, work around it by adding a patched copy of host_execute to
jit.exp, deleting the bogus line.

gcc/testsuite/ChangeLog.jit:
	* jit.dg/jit.exp (fixed_host_execute): New function, taken from
	"host_execute" in DejaGnu's dejagnu.exp, with one line removed.
	(jit-dg-test): Use fixed_host_execute, rathern than host_execute.