commits for possible 5.9.1

oliver suggested that we release a 5.9.1 since 5.10 is going to be a
while still. eric is busy for the next month, so i said i may be able to
do it myself. i am NOT officially committing to it yet since my
mood/energy for this kind of thing fluctuates so much lately, but i'm
looking into it at least

there have been 730 commits since 5.9 so there's a lot to choose from.
are there any that we would specifically like to see in a 5.9.1?

i'd prefer to avoid anything that's a 'breaking' functionality change,
that adds new shell functionality, or that will require lots of conflict
resolution

oliver mentioned pcre2, solaris/aix/haiku fixes, w/51404, and w/52509,
so i'm using those as a starting point. i'll probably include everything
i can find that improves build/test compatibility

dana