* ucontext backend (default on unix)
* setjmp backend
* fibers backend (default and required on windows)
* Fixed coroutine loop timing issues
* Fixed saving of xmm registers on x64 windows
* Fixed alignment issues
* Updated coroutine sample with cooperative fibonacci calculation.
* Disable glibc security features only when platform jump functions are used
* Removed dependency on fasm.
* Using fiber api on windows.
* Other platforms and compilers will use built in assembler and .S files or API provided by platform libc.
* Replaced stack switching procs with `coroExecWithStack()` which never returns. This makes compiler always generate proper code.
