Refactored anaysis.js.
To perform analysis in browser without recording, set window.JALANGI_MODE to 'concrete' and J$.analysis to a suitable analysis file.
To redefine all instrumentation functions, set JALANGI_MODE to 'symbolic' and J$.analysis to a suitable library containing redefinitions of W, R, etc.
Added three new API calls to *Engine.js: functionEnter, functionExit, and return_.