Wrote docstrings for subst-if and subst-if-not.
Wrote docstrings for subst-if and subst-if-not.

clasp-developers/SICL,vtomole/SICL,clasp-developers/SICL,clasp-developers/SICL,vtomole/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL