Store the stack starting address on Windows as well.
Store the stack starting address on Windows as well.

	* src/scheduler/libcoroutine/Coro.c: Stack size is allocated
	in one block on Windows, so we can get the beginning of the
	block and use it as the base stack size.
	Fix a wrong comment about x86/PPC stack grow direction.

aldebaran/libport,aldebaran/libport,aldebaran/libport,aldebaran/libport,aldebaran/libport