Added workaround for window.scrollX compat.

window.scrollX/Y is not available in IE11. As far as specifications go, is currently only specified in draft (http://dev.w3.org/csswg/cssom-view/#refsCSSOM). Falling back to 
window.pageXOffset seems like a good workaround.

On a related note; my Emscriptified project runs on IE11 although performance is very poor (mostly due to Internet Explorer itself, I think). It's pretty finicky about the shaders, as they introduced an extra set of requirements. (inout/in/out keywords not supported, can't construct mat3 from mat4, etc).
implementation of libuuid
Added comments & assert to scrollX fix.

Added comments to fix as per @kripken's request.
Added an assert too (guarded by ASSERTIONS define)
Fixed undefined check.

Forgot I had to explicitly check the type of variable type to see if it's undefined.
Added crypto quality random number generators for Node.js and browser environment if available
clean extra arg of JSify
Update library_browser.js
Update Emscripten CMake toolchain default flags to include -O2 also in compile pass, not just at link time, and add -g to CMake RelWithDebInfo builds.
do not assume callee.caller always exists
Linux fixes to emrun. Don't fail if glxinfo is not installed, and look for Chrome in 'google-chrome' executable name as well. Don't fail if browser is not found.
make sure to give Ids to split blocks in relooper
disable test_emscripten_log in spidermonkey due to breakage; issue #1970
properly handle getParameter returning null when it means a null object (e.g., no buffer is bound) and not an invalid name
fix output in glGetFramebufferAttachmentParameteriv
disable fc in default benchmarks
[SDL] Fixing SDL_UnlockSurface in IE10/IE11.

Previously, just calling SDL_UnlockSurface in IE10/IE11 would throw an exception, since Emscripten assumed that the ImageData's `data` property was Uint8ClampedArray, which has a backing buffer.

IE10/IE11 still uses the deprecated CanvasPixelArray, which does not have a backing buffer property:
https://developer.mozilla.org/en-US/docs/Web/API/CanvasPixelArray

I've added an additional path to SDL_UnlockSurface for these browsers.
release 1.8.2
Merge pull request #1971 from jvilk/sdl_fixes

[SDL] Fixing SDL_UnlockSurface in IE10/IE11
convert test_sdl_canvas to btest
disable named globals test in fastcomp