[Patch] Fix for Martin's issue

[Paolo Carlini]

Benjamin Kosnik wrote:

> Looks good to me! Thanks for fixing this up.

Thank you.
By the way, if we want to be *really* pedantic we have to give
precedence to decimal_point and thousands_sep also when looking
for the sign and the octal/hex prefix.

This has no performance implications (we do that only once) but
the code becomes definitely a little bit more ugly.

Probably, will investigate somewhat *after* having prepared the
patch for rope that I promised to Matt.

Paolo.