Math+draw optimization

+ Removed unused `var IE_VERSION`;
+ `++i` is faster on `IE8-`;
+ multiply is faster than divide on `IE8-`;
+ Math call optimization;
+ very fast `matrixMultiply()` (expanded calculations and cached common calls);
+ applied Sencha patch manually (http://dev.sencha.com/playpen/tm/excanvas-patch/);
+ manual merge with jqPlot lastest `excanvas.js` fixes (https://bitbucket.org/cleonello/jqplot/src/b233cdeb2e574e323dacd7e54eb379d20aeb3811/src/excanvas.js);
+ only `IE8-` initializes `VML`;
+ `window`, `document` and `undefined` cached for performance and better minification;
+ minor changes.