XPEG & Hyphen(-) at the Left Bound in a Class of PEG

develog - C++: Hyphen(-) should be put at the Left Bound in a Class of PEG

I caused such error again ... So, I wrote the class, sign as "[+-]".
In this case, my XPEG reported with non-straightforward message. Then I had to find the error by reading dumped trace log.

As I got burned at the error, I changed PEG format of XPEG and made XPEG allow it.

Range <- Char '-' !']' Char / Char