LEFT and RIGHT fail with an string class that extends WSTRING

[JoseRoca]

I have reworked my DWSTRING class, that extends WSTRING.
See: https://www.freebasic.net/forum/viewtopic.php?p=306682#p306682

Extending from WSTRING has solved the quirks that I had in my previous class, CWSTR, except in the case of LEFT and RIGHT, that fail with an ambiguous call error.

I have used a workaround overloading these two operators, but wanted to let you know that at least two quirks remain.