Add Perry Metzger's wrapper to run the svnserve process setgid,since this can be very helpful to svn+ssh users. Quoting from thecomments: * The idea is to avoid the problem that some interpreters like bash * invoked by svnserve in hook scripts will reset the effective gid to * the real gid, nuking the effect of an ordinary setgid svnserve binary. * Sadly, to set the real gid portably, you need to be root, if only * for a moment. * Also smashes the environment to something known, so that games * can't be played to try to break the security of the hook scripts, * by setting IFS, PATH, and similar means.* tools/examples/svnserve-sgid.c: new file.