Fix #134: Assertion failure when using specialization constants
Address #18: Add CMake option to use alternative glslang snapshot
Address #75: Replace in_releaseable_sets wioth descriptor pool create flags in DescriptorSetGroup::create()
Address #104: Pipeline cache to use for a particular device can now be specified in DeviceCreateInfo.
Address #59: Change add_vertex_attribute() to add_vertex_binding()
Fix #134: Assertion failure when using specialization constants Address #18: Add CMake option to use alternative glslang snapshot Address #75: Replace in_releaseable_sets wioth descriptor pool create flags in DescriptorSetGroup::create() Address #104: Pipeline cache to use for a particular device can now be specified in DeviceCreateInfo. Address #59: Change add_vertex_attribute() to add_vertex_binding()