Adding assignment functionality to ast.ml and parser.mly
modifies sast, semcheck, types
modifies makefile for sast,semcheck,types
Adds return types to functions.
geo
adds comments to types
modifies semcheck
combines types.ml into semcheck.ml. symbol tableand type checking done here
Commented and clarified semcheck.
Separated Tom, Emily into semcheck ops.
modified part of types section.
adds formal checking
adds return to sast
Added function and program checking.
Merge branch 'assignment_and_new_compile' of https://github.com/WHET-PLT/wdjc into assignment_and_new_compile
Minimal modification of semcheck.
Adds to to-dos.
modifies global info.
modifies sc_functions.
Some changes.