Updated ebuild

Update based on ebuild provided by Brian Evans in gentoo bugzilla
https://bugs.gentoo.org/show_bug.cgi?id=378921#c4

Previous patch to disable warnings is still applied and my custom use
flag for enabling support for database tables with 71 columns instead of
the default 25.
Remove obsolete patch.

This patch in included in mysql++-3.0-gcc-as-needed.patch