A couple of notes on the patch:

- the test_unicodedata failure was a result of computing a checksum involving str(numeric_value_of_character) for fraction characters like 1/6 and 2/3.  I've changed the test to use '{.12g}'.format(numeric_value) instead, and updated the checksum.

- the patch changes the result of format(x, ''), so that it continues to match str(x) when x is a float or complex instance.  So when there's no typecode and no precision given, float formatting behaves like repr/str;  when there's no typecode but a precision *is* given, float formatting behaves like 'g' formatting, but always ensures at least one digit after the point for a result in non-scientific format (as before).

This change involves some slightly messy logic in formatter.h (which now needs to pass type 'r' to PyOS_double_to_string in this case);  there may be a better way to write this code.  Eric, if you have a chance to look at the formatter.h changes, I'd appreciate your comments.