[patch] Fixes for kdelibs on win32/msvc

[Maksim Orlovich]

>
> Hello,
> RFC. This patch is against trunk from the last weekend, so I'll update it
> before commiting.

This change to KJS:
-    static const uintptr_t TagMask = 3; // type tags are 2 bits long
+    static const uintptr_t TagMask;

is NOT ok, as this constant is accessed in some ultra-hot paths. If you
have to workaround this bug in your compiler, please use an enum.

Also, could you please consider disabling the bogus "casting int to bool
is slow!" warning rather than adding tons of extra conditionals to the
code?

-Maks.