libm long double functions on ARMv6.

[Kyle Evans]

Alright, apologies for the noise. I answered my own question- went
through the `long double` functions from msun/Makefile:101, and found
that `fmodl` seems to be the only one that is not properly aliased.

The issue at [1] (r199422) seems to be relevant, so I'm CC'ing both
emaste@ and ngie@ as interested parties, also hoping for some
$0.02USD.

I'm inlining a proposed patch at the end of this e-mail to match what
is currently done for all of the other `long double` functions on
these platforms where long double == double.

[1] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=199422

diff --git a/lib/msun/src/e_fmod.c b/lib/msun/src/e_fmod.c
index 720aa03..a3578a1 100644
--- a/lib/msun/src/e_fmod.c
+++ b/lib/msun/src/e_fmod.c
@@ -130,3 +130,8 @@ __ieee754_fmod(double x, double y)
        }
        return x;               /* exact output */
 }
+
+#if LDBL_MANT_DIG == 53
+__weak_reference(fmod, fmodl);
+#endif