Replace the this pointer with a local var for denser packing

[Joe Wieloch]

It would be nice if ... the packager replaced the this pointer with a one character local variable in functions, saving three characters per "this" use.

The only problem I can think of is if a function is nested inside another function. In that case a separate local variable definition should be used inside that function for the this pointer (it might be being assigned to a different object).

The definition takes up space so it only makes sense for functions that have five or more this pointers.

[Piotrek Koszuliński]

Since 4.0 CKBuilder uses Google Closure Compiler so:

• we can't easily modify its behaviour,
• it uses very complex algorithms for optimization, so we don't have to add ours,
• such a micro optimizations very often doesn't work well with gzip.