conditional make include
README tweaks
another README tweak
bringing back some old behavior
don't have to non-zero exit here
better null return
Revert "don't find replacements for labels either"

This reverts commit ed8258a5c4f50ae4ee9ca485afc134322d5f39ef.
Revert "bringing back some old behavior"

This reverts commit cea166afb69ea68eea9fc118b4f6861aae9e9c18.