commit: add keep-alives for those that need conversion to pointer receivers
commit: add keep-alives for those that need conversion to pointer receivers

We can't work on the copies here, we need to have pointer receivers so we know
we're keeping alive the object whose finalizer would free the unmanaged memory
we're working with.

ezwiebel/git2go,libgit2/git2go,ezwiebel/git2go,clns/git2go,clns/git2go,libgit2/git2go,clns/git2go,ezwiebel/git2go,libgit2/git2go,pks-t/git2go,pks-t/git2go