mutable decl syntax change

examples/programs/mutable_global/main.bro

@@ -2,11 +2,11 @@ Point :: struct {
 	x i32
 }
 
-counter int = 0
-ratio float = 1
-span range = 0..2
-point Point = Point { x = 1 }
-values [_]mut i32 = [10, 20]
+counter := i32(0)
+ratio := 1.0
+span := 0..2
+point Point := Point { x = 1 }
+values [_]mut i32 := [10, 20]
 
 bump func(value @mut i32) void {
 	value^ += 1
@@ -19,7 +19,7 @@ main func() i32 {
 	point.x += counter
 	values[1] = point.x
 
-	total i32 = counter + point.x + values[1]
+	total i32 := counter + point.x + values[1]
 	for span |i| {
 		total += i
 	}