Feature to enable asynchronous event driven of network events
replace 111 error code literal with ERRNO_CODES.ECONNREFUSED as prompted by juj
Improve callback mechanism to allow an arbitrary userData pointer to be passed during callback registration that will subsequently be passed to the callback
Improve error handling on getsockopt when a level other than SOL_SOCKET or an optname other than SO_ERROR is supplied as per the conversation with juj
Make debug message for the default logging on error handler use Module.printErr rather than Module.print as suggested by juj
Add some more documentation to emscripten.h to explain that the JavaScript error callback takes an array containing the file descriptor, error code and error message.
by default, require that subcommands actually succeed.  there were scenarios where compiler.js or js-optimizer.js would fail, but emcc would happily try to continue, and sometimes succeed, causing corrupted builds.
Remove sdl_ttf from sdl_mouse test

sdl_ttf isn't being used at all.
many tests depend on commands failing
Remove the Emscripten leak check superfixture stuff: it's not compatible with asm.js or fastcomp, sadly.
minor refactoring in support of an upcoming optimization
Port TypeID arrays to use constexpr static arrays so that they're initialized in the static data segment and reduce resulting JavaScript code size.

Conflicts:
	system/include/emscripten/wire.h
Shave a bit more time off by forcing inlining of things that will never be merged with other functions.
Remove a bunch of cleverness.  Turns out you can generate constexpr arrays.  :P
update to use cryptographic random if it is available

optimize cryptographic random generator.
Fix CMAKE_FIND_ROOT_PATH

This allows projects and libraries using CMake to automatically find include directories and library files in the emscripten system directory. I am unsure why it was set to `${EMSCRIPTEN_ROOT_PATH}/cmake` before, but I tested it and it didn't work until I changed `cmake` to `system`. `CMAKE_FIND_ROOT_PATH` is documented [here](http://www.cmake.org/Wiki/CMake_Cross_Compiling#Searching_and_finding_external_software).
Merge pull request #2447 from usagi/dev-urandom-update

update to use cryptographic random if it is available
optimize crypto.getRandomValues usage a little
Merge pull request #2454 from chadaustin/jsrun-fail-if-error

by default, require that subcommands actually succeed.  there were scena...
Merge pull request #2458 from chadaustin/embind-constexpr-typeid-array

Code size reduction: use static constexpr arrays to define signatures