relocatable-prog-wrapper: Fix possible link error. * m4/setenv.m4 (gl_FUNC_SETENV_SEPARATE): Move determination of HAVE_SETENV and REPLACE_SETENV and AC_LIBOBJ invocation from here... (gl_FUNC_SETENV): ... to here. * m4/canonicalize.m4 (gl_CANONICALIZE_LGPL_SEPARATE): Update comment. * m4/readlink.m4 (gl_FUNC_READLINK_SEPARATE): Likewise.