remove `__doc__ =` and fix tweak doc diffs
Correct file reference (there's no qstrraw.h)
Simplify detection of quote characters in mp_str_print_quoted.

Once a double quote has been found, the subsequent discovery of a single quote
won't change behaviour at all, so don't bother looking for one.
Merge pull request #655 from Rosuav/master

Two small changes
Merge pull request #650 from bvernoux/master

micropython port for HydraBus
Merge pull request #653 from Metallicow/switch-example-correction

remove `__doc__ =` and fix tweak doc diffs