First codegen commit - generate .text section
Add type_id (return low level type) from monga type

Add type_size to return low level monga size
Fix declaration -> declaration list linkage
Fix Var definition

Var: ID | exp [exp]
fill declaration offsets on typechecking routine
Fix var array node construction
Fill declaration offsets
Pertial implementation

Exps (not all), Var, Functions, export_to_int,
jmp_if_false, jmp_if_true, cmd assignment,
cmd return
Configure parameters offset
Support: calls and arithmetic unary minus expression

Fix generated assembly
last commit header changes
simplify main spec
add helper function to print integers
Examples to stuy
Support "extern" function declarations
Support call commands and extern calls
Add generate_expression_val and fix binary sum
Improve binary expressions code
Fix CmdRet - return expressions - constants or variables
Support binary expressions with variables