Add Portuguese and Brazilian Portuguese localizations.

Update language code format to allow region specifiers (like pt-br).
Merge branch 'portugese' of https://github.com/mattflaschen/MathJax into issue491
Remove duplicate "pt" data and implement language remapping, escape non-ASCII letters, replace dot by comma in brazilian numbers. Fix issue #491 and #492

Conflicts:
	unpacked/MathJax.js
Merge branch 'issue491' into i18n