1. Use uctypes.bytearray_at().
Implementation of the "ffi" module predates that of "uctypes", so
initially some convenience functions to access memory were added
to ffi. Later, they landed in uctypes (which follows CPython's
ctype module).
So, replace undocumented experimental functions from ffi to
documented ones from uctypes.
2. Use more suitable type codes for arguments (e.g. "P" (const void*)
instead of "p" (void*).
3. Some better var naming.
4. Clarify some messages printed by the example.
A shorter name takes less code size, less room in scripts and is faster to
type at the REPL.
Tests and HW-API examples are updated to reflect the change.
This follows the pattern of how all other headers are now included, and
makes it explicit where the header file comes from. This patch also
removes -I options from Makefile's that specify the mp-readline/timeutils/
netutils directories, which are no longer needed.
The -ansi flag is used for C dialect selection and it is equivalent to -std=c90.
Because it goes right before -std=gnu99 it is ignored as for conflicting flags
GCC always uses the last one.
Just one sample is updated with on()/off() for now, there should be
remaining sample(s) showing .value() use (but more can be converted later,
as long as 1 or so good samples of .value() remains).