Added docstrings for subst, nsubst, subst-if, nsubst-if, subst-if-not, and nsubst-if-not.
Added docstrings for subst, nsubst, subst-if, nsubst-if,
subst-if-not, and nsubst-if-not.

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