Avoid to generate duplicated variable name

[fummicc1]

Overview

If mockable has multiple initializer which have same parameter name, output mock can't be built due to conflict of variable name.

This fix aims to solve #224 .

After fix

• Input

/// @mockable
protocol MyProtocol {
    init(param: Any)
    init(param: String)
    init(param: any Sequence<Character>)
}

• Output

class MyProtocolMock: MyProtocol {
        private var _param: Any!
    init() { }
    required init(param: Any) {
        self._param = param
    }
    required init(param: String = "") {
        self._param = param
    }
    required init(param: any Sequence<Character>) {
        self._param = param
    }

}