As I suspected for a long time, for x86, register helper doesn't really make
any difference - there's simply not enough register to keep anything in
them for any prolonged time. Anything gets pushed on stack anyway. So, on
x86, uPy passed all tests even with empty reg helper. So, this setjmp
implementation goes as "untested".
Blanket wide to all .c and .h files. Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.
Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.
