Define what polyfills to include in the Makefile

The Makefile now lists the polyfills to include. These files register
themselves and then the polyfills.js initializes the polyfills for The
given global.

Fixes #1244
Actually I don't understand why you have to list the files rather than import the modules with polyfill-import.js. I guess you think it is easier to customize the makefile rather than the polyfill-import.js?