added inline support

[yuta1228]

Found couple of problems regarding support for inline helper.

• Inline helpers are recognized as T_ESCAPED/T_UNESCAPED/T_UNESCAPED2 so argument parts are not recognized.
• Arguments are not handled as array, therefore multiple arguments were not possible.

I tried to address these issues by following codes. I suppose its better to define new tag type if possible, but I was not able to come up with nice way to differentiate the regular variable to inline helper in the scanning phase.

Even though, unescaped/escaped version of syntax works in this code, both should return same thing.

[yuta1228]

let me close this one first and do it again. sorry.