Mismatch between sizeof(Partio::ParticleIndex), sizeof(size_t), sizeof(int)

[StefanBruens]

There is some assumption Partio uses size_t for its index type:

OpenShadingLanguage/src/liboslexec/pointcloud.cpp

Lines 360 to 365 in 7e34ce2

	// RS::pointcloud_search takes size_t index array (because of the
	// presumed use of Partio underneath), but OSL only has int, so we
	// have to allocate and copy out. But, on architectures where int
	// and size_t are the same, we can take a shortcut and let
	// pointcloud_search fill in the array in place (assuming it's
	// passed in the first place).

which is apparently wrong (for the last 12 years):
https://github.com/wdas/partio/blob/7cb3743c6e19c04ac049c05f8f81af2f24410ea3/src/lib/Partio.h#L55
typedef uint64_t ParticleIndex;

On 32 bit archs the compilation then fails due to:

OpenShadingLanguage/src/liboslexec/pointcloud.cpp

Lines 114 to 118 in 7e34ce2

	static_assert (sizeof(size_t) == sizeof(Partio::ParticleIndex),
	"Partio ParticleIndex should be the size of a size_t");
	// FIXME -- if anybody cares about an architecture in which that is not
	// the case, we can easily allocate local space to retrieve the indices,
	// then copy them back to the caller's indices.

Wouldn't it be better change it to unsigned long* out_indices in RendererServices::pointcloud_search? (This may require a version bump for 64bit archs, but only if size_t != unsigned long. For 32bit archs, the current code does not work anyway). Dito for pointcloud_get.