Potpourri of small improvements to code size and perfomance

[flesler]

Hi, this diff contains a large set of small changes that make the code slightly shorter. Some might make the code faster.

Most are redundant vars, or redundant ifs. Also declared undefined as local var and replaced all null for undefined, this should be slightly faster, and make the code much smaller.

I exposed the speeds hash (slow,fast), so it can modified/extended. I don't remember them all, but their are mostly small changes.

I ran the test suite on IE6 and FF2 and it passed.

[flesler]

Some more possible changes described

[scott.gonzal]

The local undefined variable is faster than the global undefined property, but slower than null. I think keeping the local undefined variable is a good idea, but null should be used where possible.

[joern]

Sounds like both variations should be send through the benchmark.

[flesler]

I wasn't really sure about the undefined part, I just added, then you can decide. There're many small changes, you don't need to take them all, some don't even require testing.

[flesler]

Added most of these changes at [5357]