Remove genIRFileText from GenJSFiles.

It's been useless since we had scalajsp.
Merge pull request #847 from sjrd/fix-printer-undefined

Fix printing of 'void 0' as '(void 0)'.
Merge pull request #848 from sjrd/small-cleanup

Remove genIRFileText from GenJSFiles.
Add a field optimizerHints in ClassInfo.
Mark anon functions, @inline classes, and ref classes as inlineable.