Test with Acorn (not Acorn-6to5) and fix issue with AssignmentPattern

[zjmiller]

Acorn-6to5 is not up-to-date. After switching to Acorn, a test failed, showing that escodegen had been improperly handling AssignmentPattern.

[zjmiller]

When dealing with the AssignmentPattern node type, escodegen was trying to use an operator property. But AssignmentPattern doesn't have an operator property. The tests weren't noticing this because the only relevant tests (compare-acorn-es6) were using Acorn-6to5 instead of Acorn. Acorn-6to5 isn't up-to-date and it wasn't parsing these cases correctly. So two mistakes (one in escodegen and one in Acorn-6to5) were essentially canceling each other out as far as the tests were concerned. Switching to the more up-to-date Acorn resulted in the relevant tests failing.

[michaelficarra]

Nice, thanks.

[GabrielRatener]

The issue with AssignmentPattern still appears to be present in version 1.6.1