Local variables shadowing

Starting with version 0.9.K.0, local variable shadowing is part of vJass syntax, unlike Jass syntax in which it has always been a problem. Up to patch 1.24, it was not even possible to shadow more than one variable, and it turned the whole map script into case-insensitive. These glitches were apparently fixed around patch 1.24, but they were fixed barely to a level of helping GUI users do local var tricks. Issues persist, and the issues are of the kind that could eventually cause some scripts issues in unpredictable places.

If the vJass code is used correctly and things are correctly scoped, this should not be a problem. However, when using code from multiple places, one of the codes may not be correctly scoped, which threatens to cause a conflict with a local variable and thus then making your map mysteriously unopenable in wc3. Jass' weakness with variable shadowing was too unpredictable in nature. So I decided to add a small preprocessor phase to jasshelper that will simulate correct local variable shadowing. This means that the local variables in your functions may now have the same name as any global in the map (even globals you do not know about) without causing further issues or unknown, unpredictable bugs (unlike normal Jass in which this is an active possibility). Although the vJass code allows variable shadowing, it is compiled to Jass code in which there is no shadowing (some l__ prefixes are added to conflicting local variables).