Better is_circular function detection

[amir734jj]

• formal inside KEYcase_stmt is circular if KEYcase_stmt's expression is circular and formal type is extending LATTICE
• Use of actual is circular if formal and actual have the same type and the type is extending LATTICE
• Use of return of function call is circular if type of LHS and return type of function call are equal and extending LATTICE
• prevent simple edge from function_decl$result -> LHS
• To detect if the declaration is circular, IF MOD (modifier) is not null then we say edge is monotone

Tested on:

• all aps examples (first/follow/nullable/nested-cycles/cool-circular-semant and etc)