Created attachment 402376 [details, diff] Patch of boost.m4. Will not work without eautoreconf cclive-r1 fails to compile with gcc-5, because it uses an outdated version of boost.m4. I attach a backported part of the correpsonding patch from boot.m4 upstream (although a simpler patch would be to just add -P to the preprocessor call). Anyway, the patch is not really tested, because it requires to call eautoreconf to the ebuild to which I had to time yet. I used an alternative fix (which thus is tested): Add -P to CPPFLAGS.
Created attachment 402612 [details] build log
http://gitweb.gentoo.org/repo/gentoo.git/commit/?id=3ae39c3d04203862680a9b776393aec91a46285c