boinc-client dependencies

[Andreas Obermaier]

Hello port maintainers,

I use boinc-client on 10.1-RELEASE-p6.  I found that at least one MilkyWay at Home
task needs libstdc++.so.6, so I had install lang/gcc to make it work.

Mabye it makes sense to add lang/gcc as a dependency for boinc-client or just add a note
that some BOINC projects or project tasks might require it.

Thanks for your time.

Best regards,

Andreas Obermaier