Symbol Table Work and fixes to calc3a.c

- Changed the Calc3.y file to insert type and size into the symbol
table.
- Changed calc3a.c to attempt to print floats correctly and to
recognize type by symbol table entry
Merge branch 'master' of https://github.com/dpenning/f13-calc
(calc3p.c) remove print statements
Partial implementaion of pstack output
add basic assign op and !=