checker: fix global fn calls

vlib/v/ast/scope.v

@@ -28,12 +28,14 @@ pub fn (s &Scope) free() {
 	}
 }
 
+/*
 pub fn new_scope(parent &Scope, start_pos int) &Scope {
 	return &Scope{
 		parent: parent
 		start_pos: start_pos
 	}
 }
+*/
 
 fn (s &Scope) dont_lookup_parent() bool {
 	return isnil(s.parent) || s.detached_from_parent

vlib/v/checker/checker.v

@@ -2407,6 +2407,15 @@ pub fn (mut c Checker) fn_call(mut call_expr ast.CallExpr) ast.Type {
 			}
 		}
 	}
+	// global fn?
+	if !found {
+		if obj := c.file.global_scope.find(fn_name) {
+			sym := c.table.get_type_symbol(obj.typ)
+			if sym.kind == .function {
+				found = true
+			}
+		}
+	}
 	if !found {
 		c.error('unknown function: $fn_name', call_expr.pos)
 		return ast.void_type