Implemented assert keyword

src/build/core/Function.go

@@ -14,11 +14,13 @@ type Function struct {
 	Body      []token.Token
 	Functions map[string]*Function
 	Err       error
+	deferred  []func()
 	count     counter
 }
 
 // counter stores how often a certain statement appeared so we can generate a unique label from it.
 type counter struct {
+	assert    int
 	branch    int
 	data      int
 	loop      int