Remove extra commas from webgl-debug.js

This is done to improve compatibility with Closure compiler.
Make webgl-debug.js handle clear better

This change makes WebGLDebugUtils to be able to log clear calls better, by
separating the parameter into its bitwise-orred components if it is valid.
Unify indentation in webgl-debug.js

Change the tabs used for indentation to spaces and align indented blocks to two
spaces.
Merge pull request #755 from Oletus/webgl-debug-improvement

WebGLDebugUtils improvement