Replace the timer-based sleep with the standard win32 call since the former
has no benefits: even though it allows specifying the time in 100uSec
chunks, the actual resolution is still limited by the OS and is never
better than 1mSec.
For clarity move all of this next to the mp_hal_delay_ms definition so all
related functions are in one place.
If this is not set it might default to calls to open() to use text mode
which is usually not wanted, and even wrong and leading to incorrect
results when loading binary .mpy files.
This also means that text files written and read will not have line-ending
translation from \n to \r\n and vice-versa anymore. This shouldn't be much
of a problem though since most tools dealing with text files adapt
automatically to any of the 2 formats.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
