package/boost: add patch to fix libquadmath issue

Backport patch from upstream [1] to fix build issues with toolchains not
providing libquadmath, but still supporting __float128.

Fixes:
http://autobuild.buildroot.net/results/fcc/fccb40e7b05b84275cfe36a890cedbbaaaa4f953/
http://autobuild.buildroot.net/results/cfc/cfcc6c44d2225b9baf0fd92d3cfba4922bfb248b/
http://autobuild.buildroot.net/results/ab1/ab1a5aceedb7f9edcd5536b601f1ffb66c5fe1e8/
http://autobuild.buildroot.net/results/1ed/1ed3c1ae1e31325b49dd05c1f616637bb5e6382d/
http://autobuild.buildroot.net/results/9e5/9e53a5aff9966c6f26e705c91d13692107452feb/
and many more.

Backported from: 74ff2db959c5fa75bec770c41ed2951a740fe936

[1]
https://github.com/boostorg/math/commit/74ff2db959c5fa75bec770c41ed2951a740fe936



Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>