Add strings to bison grammar tokens.
Add strings to bison grammar tokens.

This ensures that any syntax errors passed to the parser are printed
using the string reprentations of the tokens rather than their name.

New:
    SDC Error line 16 near '-max': syntax error, unexpected -max, expecting -from or -to or EOL

Old:
    SDC Error line 16 near '-max': syntax error, unexpected ARG_MAX, expecting ARG_FROM or ARG_TO or EOL

kmurray/libsdc_parse,kmurray/libsdc_parse,kmurray/libsdcparse,kmurray/libsdcparse,kmurray/libsdc_parse