Some fixes for compilation errors and warnings on different platforms.

[Mr-Question]

Fix for redefinition of variables in nested scope; Fix fatal error: 'malloc.h' file not found on MacOS; Fix for the following warnings on Linux:

• unused variable;
• suggest parentheses around '&&' within '||';
• comparison between signed and unsigned integer expressions;
• deleting object of polymorphic class type 'CDelaBella' which has non-virtual destructor might cause undefined behaviour.

[cschreib]

Thanks for the PR, it's a shame this has not been merged yet.

FYI, the PR also doesn't go as far as it could. On my platform, I get tons of warnings for "old-style" (C-style) casts. I also get the more dangerous cast from 'const void *' to 'CDelaBella::Vert *' drops const qualifier on line 104 and 105.

But perhaps the most annoying to me is the warning coming from delabella.h: 'IDelaBella' has virtual functions but non-virtual destructor, which shows up when I compile my own code (in virtue of it being in the header).

If you want to include these fixes in your PR, I'd be happy to use your fork while this gets merged :)

[msokalski]

I'm closing it now, there are too many conflicts with hybrid branch which is going to be merged soon. Anyway thanks for your time fixing these warnings :)