fix(Array.Prototype): ease Array.prototype pollution by using Object.defineProperty (#980)
fix(Array.Prototype): ease Array.prototype pollution by using Object.defineProperty (#980)

fix #980

this apparently prevents a conflict with pdf.js.
patch given by @brice81 in #980.
reformatted, added comment

opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay