Before this change, if REPL blocked executing some code, it was possible
to still input new statememts and excuting them, all leading to weird,
and portentially dangerous interaction.
TODO: Current implementation may have issues processing input accumulated
while REPL was blocked.
This is a convenience function similar to pyexec_file. It should be used
instead of raw mp_parse_compile_execute because the latter does not catch
and report exceptions.
In other words, unix port now uses overriden printf(), instead of using
libc's. This should remove almost all dependency on libc stdio (which
is bloated).
Paul Sokolovsky
Damien George