Inline methods of IndexedSeqOptimized in an ad hoc way.

Just because.
Inline more simple methods.
Discard VarDefs that are not actually used.
Print some trees differently in IR mode than in JS mode.
Print Undefined() as 'void 0' instead of 'undefined'.

It is typically faster, and actually more correct.
Discard side-effect-free LoadModules if not used.
Merge pull request #839 from sjrd/inline-more-methods

Inline more methods
Fix #831: Set Character.MAX_VALUE to correct value
Merge pull request #840 from sjrd/discard-useless-things

Discard useless things
Merge pull request #841 from sjrd/printer

Improve the IR/JS printers
Merge pull request #842 from gzm0/fix-char-max-value

Fix #831: Set Character.MAX_VALUE to correct value
Fix detection of elidable module accessors.
Merge pull request #844 from sjrd/fix-elidable-module-accessor

Fix detection of elidable module accessors.
Adapt checksizes after the improvements to the optimizer.
Merge pull request #845 from sjrd/update-checksizes

Adapt checksizes after the improvements to the optimizer.
Fix partests with the optimizer.
Merge pull request #846 from sjrd/fix-partests-with-optimizer

Fix partests with the optimizer.
Fix printing of 'void 0' as '(void 0)'.
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)'.