Restored unit tests for ± parsing: this feature will be implemented.
Removed unnecessary _* variable (__all__ is used by pydoc and import *).
More precise documentation: non-Unicode strings with ± are not recognized (this would entail guessing an encoding).
Working: ± ufloat_fromstr() parsing now works. Removed debug message.
To do: make the code simpler.
Extended ufloat_fromstr() so that it works on u'3.14±0.1'.
Added the fact that expressions like (3.1±1e-5)e2 can be parsed too. This
may prove useful. This could even be useful for parsing back a future
formatted output (maybe the output of the .3g/.3G/.3n formats, if the current
semantics changes).