gracefully handle ExitStatus exception in async main loops
Improve CMake toolchain file to use response files. Avoid the compiler detection mechanism that could throw CMake off depending on what is in Windows PATH. Use CMAKE_EXECUTABLE_SUFFIX to specify whether to build .html or .js.
Utilize EM_BUILD_VERBOSE in other.test_cmake.
Delete Emscripten_unix.cmake, the previous commit makes that obsolete!
Add a test to ensure that EMSCRIPTEN=1 variable is set in CMake when building.
Fix other.test_cmake when EM_BUILD_VERBOSE is not defined.
Remove the need to pass CMAKE_MODULE_PATH to CMake by weakly setting it in the toolchain file.
Remove the old mechanism of generating a CMake toolchain file on the fly when 'emconfigure cmake' is called. Instead, the Emscripten toolchain file in Emscripten\cmake\Platform\Emscripten.cmake is always used. This unifies the CMake toolchain handling to use the same toolchain independent of how CMake gets invoked.
Have test_cmake also test that running 'emconfigure cmake' works, in addition to running cmake directly.
Remove default filename suffix specification in CMake toolchain, since test_openjpeg will then fail to configure.
Adjust EM_BUILD_VERBOSE environment variable to take values 0,1,2 or 3, with the following meanings:

0 - No verbose build. Emscripten will mute stdout and stderr invokations of external tools (configure, cmake, make). Stdout and stderr of those runs will be logged to file (the old mechanism)
1 - Print stderr.
2 - Print stderr and stdout.
3 - Print stderr and stdout, and invoke make with VERBOSE=1.
Document tests in test_cmake.
Use logging.error() instead of print >> sys.stderr in test_cmake to report errors.
initial setup for proxying: add option and generate separate html and js
stubs for proxied getImageData/putImageData
proxy window.close
proxy canvas writes
add test harness support for proxying, test_sdl_canvas_proxy passes
test file preloading in worker
stub out console in proxied worker