py/mphal.h contains declarations for generic mp_hal_XXX functions, such
as stdio and delay/ticks, which ports should provide definitions for. A
port will also provide mphalport.h with further HAL declarations.
If VT100 support is not available then a given implementation of
mp_hal_erase_line_from_cursor might need to know the number of characters
to erase.
This patch does not change generated code when VT100 is supported, since
compiler can optimise away the argument.
Paul Sokolovsky
stijn
Damien George