Add iOS 10 support for TerserPlugin (#6067)
Add iOS 10 support for TerserPlugin (#6067)

Resolves #5630
zeit/next.js,zeit/next.js,flybayer/next.js,flybayer/next.js,JeromeFitz/next.js,azukaru/next.js,JeromeFitz/next.js,JeromeFitz/next.js,azukaru/next.js,zeit/next.js,BlancheXu/test,BlancheXu/test,azukaru/next.js,BlancheXu/test,flybayer/next.js,flybayer/next.js,azukaru/next.js,JeromeFitz/next.js