Blender Git Loki

Render API: Fix bugs regarding pass handling when Cycles debugging is enabled

The probem here was that regular passes are stored as (signed) integers.
Therefore, the pass with bit 31 set (the Cycles debug pass) is stored as -1.
On its own, that's fine - however, when that pass type is implicitly cast to uint64_t
in a function call, the compiler apparently first sign-extends it and then reinterprets
it as unsigned, so the result is 0xffffffff80000000 instead of only bit 31.
To get around that issue, the type is now explicitly cast to a unsigned int32 first and
then implicitly extended to uint64_t.