gracefully handle ExitStatus exception in async main loops
 - added readFile and writeFile helpers
 - added default modes to mkdir / mkdev
updated unistd and fs_base tests to use new FS APIs
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.
Remove unused / unwritten emlibtool.

This isn't used or even implemented and apparently isn't necessary.
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.
rearranged FS function order
Improve emscripten to autodetect the temp directory even if TEMP_DIR is not present at all in ~/.emscripten. Add sanitation to TEMP_DIR handling to detect that the path exists. Paths like TEMP_DIR='/tmp' and TEMP_DIR='c:\temp' will now print out a descriptive error message on Windows. (proper form is TEMP_DIR='c:\\temp' or TEMP_DIR='c:/temp' on Windows). Fixes #1292.
When running out of memory and growing heap size is not allowed, actually print out what the current value of TOTAL_MEMORY was the application was built with, to help estimate how much memory might be needed.
Merge pull request #1593 from juj/TEMP_DIR_check

Temp dir check
Merge pull request #1586 from waywardmonkeys/remove-emlibtool

Remove emlibtool
add long double aliases for a lot of things.

__fpclassify and __signbit are handled in another patch on the
libc header replacement branch.