An initial attempt at variables and questionable_return_t cleanup

Unfortunately, it doesn't parse...
F*x scanning and parsing of variables

They still don't show up in the hashtable, however...
Copy (and leak) yytext buffer when copying variable names
Fix questionable_return_props() errors in indirect vs. direct and cleanup vs. don't
Fix reversed indirect logic in the binary operator implementations that always used to work
Fix reversed operand order during variable code generation
Fix missing comma in last binary operator case
Always copy variables into temporaries b4 using (to avoid accidental overwrites)

This also sets their cleanup property to true so that the extra copies aren't retained.
Merge branch 'variables'

Conflicts:
	et.l.l
	et.y.y
Create README.md