Fix up AST-to-source, add a few transforms
Fix up AST-to-source, add a few transforms

particularly, lexical variables are sometimes not in the dictionary, so they'd
sourcify as NIL, which is no good.

The added ones are m-v-c, l-t-v, fdefinition, symbol-value, the, go, block,
return-from, tagbody.

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