Commit 5b8e6f85 introduced stubs for three functions that make no sense
for git-shell. But those stubs defined libgit.a functions a second time
so that a linker can complain.
Now git-shell is only linked to a subset of libgit.a.
Signed-off-by: Stephan Beyer <s-beyer@gmx.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>