nanogui: Thread: [patch] eliminate warnings for x11/i386 native compile

Hello,

attached patch kills most (if not all - not all libs checked!)
warnings in the 0.91 tree when compiled for x11 on native i386.

The only sub optimal solution concerns the mapping from RECT
to the LPPOINT type where a (void*) type cast was my solution.

(((-details-
the best solution could be usage of unnamed struct/unions
inside of RECT which looks something like this:

  typedef struct {
    union {
      MWPOINT left_top;
      struct {
        MWCOORD left;
        MWCOORD top;
      };
    };
    union {
      MWPOINT right_bottom;
      struct {
        MWCOORD right;
        MWCOORD bottom;
      };
    };
  };

(please compare to mwtypes.h)
This would make it all clear and resolveable with current GNU C
but risk is high that other compilers and old GNU C will fail
on this, so better dont touch such highly critical header files.
-details-)))

Other changes should all be purely internal
and some are even rather evident additions
to Nano-X and demos so no special comment on them 
besides this: they do kill a few build warnings.

-Alex.