RFC: run testsuite with -O3

[Tom Tromey]

>>>>> "Andrew" == Andrew Haley <aph@redhat.com> writes:

Andrew> Well, if you really expect to see regressions at -O3 that don't
Andrew> trigger at -O1, fair enough.  But know this: the longer the tests
Andrew> take, the less they will be run by developers.

True.  Another question is the overlap between -O and -O2 (versus -O3,
which I gather is "more different").  We already build the library
with -O2...

Let's go ahead and remove -O and add -O3.

Tom