Use of global MODE before declaration caused uglify problem

[djehring]

The global variable MODE is used in the code before it is declared. When this package is passed through js-uglify it breaks as these lines:

if (frame.multiline_frame ||
frame.mode === MODE.ForInitializer ||
frame.mode === MODE.Conditional) {
return;
}

are not parsed to use the uglified constants MODE_ForInitializer and Mode_Conditional.

Moving the declaration of mode before its use fixes this problem.

[bitwiseman]

@djehring Can you submit a PR?