perl with -Duselongdouble needs more libm support

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

When compiling perl on NetBSD with -Duselongdouble, some functions are
missing.

The perl people found that out themselves:

https://rt.perl.org/Public/Bug/Display.html?id=134376

here's the smoke test on NetBSD 8.1:

http://perl5.test-smoke.org/report/93329

Reading the output, there seems to be at least "expm1l", "log1pl",
"log2l", and "tgammal" missing.

Also, there is an unexpected result:

# rp = 0xa., ep = 0xa. (rh df85458a2bb48p-2, eh df85458a2bb4a9bp-2)
# re = p-2, ee = p-2 (rh df85458a2bb48, eh df85458a2bb4a9b)
# (rh 8, eh a9b)
# (rh 80, eh a9b)
not ok 1459 - '%a' '2.71828182845904509' -> '0xa.df85458a2bb48p-2' cf '0xa.df85458a2bb4a9bp-2'

perhaps a bug in our libm?

(I haven't tried this myself, it was just pointed out to me and I hope
for sympathetic ears & coders ;) ).
 Thomas