Minor mw.loader fixes

Minor mw.loader fixes
- No functional changes
- Whitespace correction
- Comment fixes
- Combine var statements
- A few [[JSPERF]]ies
- Using mw instead of mediaWiki
- Putting global alias on top, to avoid a ReferenceError in case the immediately invoked "new function(){}" refers to mw during the construction
- "class" -> "constructor"
- caching "typeof dependencies" in mw.loader.using
- fix var "group" collision in mw.loader.work
- move var statements to top of functions
- fixing some occurrences of var statements in for-loops by declaring them before the loop
- Remove space before slash in html-fragement for jQuery html regex in <link /> and <br />