Release (v0.4.4)

Changes in this patch release:

• Added new dr.prefix_sum operation for inclusive and exclusive prefix sums 4be7aa0
• Added new dr.scatter_inc operation for stream compaction 754a541
• Fix dr.dispatch when a instance of the class has been deleted 1f908cc
• Support for dr.PCG32 samplers in recorded loops' state 58c8485
• Extend dr.binary_search to additionally support non-scalar and multi-dimensional indices 79de06a .. 5fc5750
• Fix race condition in jit_sync_thread() 6690923
• Switch jitc_vcall_prepare() allocation method to avoid deadlocks c13ef93
• Various minor bug fixes