allow unary operators as the first token after if or while

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rhai"
-version = "0.6.0"
+version = "0.6.1"
 authors = ["Jonathan Turner", "Lukáš Hozda"]
 description = "Embedded scripting for Rust"
 homepage = "https://github.com/jonathandturner/rhai"

src/parser.rs

@@ -191,6 +191,8 @@ impl Token {
             Or               |
             Ampersand        |
             And              |
+            If               |
+            While            |
             Return => true,
             _ => false,
         }