add if-else statement (#7)

add if-else statement (#7)

* add define statement for equity

* add test

* add if-else statement

* handle with stack

* optimise parameter reference check

* optimise else label

* optimise ifbody stack

* optimse compile if else statement

* check math for count

* add unit test

* optimise parse ifstatement

* after endif support add statements

* add sequese for ifstatement

* add test

* rm redundant modify