* Update release number to 81.
Public Issues:
* Fix missing "`valid`" phrasing in some obscure cases (public pull
request 605).
* Replace improper use of cannot: referring to the implementation in the
description of the
<<features-limits-maxUpdateAfterBindDescriptorsInAllPools,
pname:maxUpdateAfterBindDescriptorsInAllPools>> limit (public pull
request 738).
* Reorder description of bits in elink:VkPipelineStageFlagBits and the
<<synchronization-pipeline-stages-supported, Supported pipeline stage
flags>> table to match their definition order (public pull request 740).
* Add description of ename:VK_BUFFER_USAGE_CONDITIONAL_RENDERING_BIT_EXT
to elink:VkBufferUsageFlagBits (public pull request 741).
* Fix value usage statement for slink:VkSubpassDependency stage mask
parameters (public pull request 742).
* Fix visible markup in registry schema document (public pull request
#745).
Internal Issues:
* Make the <<geometry-invocations, geometry shader invocation
description>> and <<shaders-geometry-execution, Geometry Shader
Execution>> descriptions consistent with other pipeline stages (internal
issue 1325).
* Mark the `VK_NV_glsl_shader` extension as deprecated.
* Adjust the per-instance vertex attribute offset formula specified by
`VK_EXT_vertex_attribute_divisor` for
slink:VkVertexInputBindingDivisorDescriptionEXT so that the interaction
between pname:firstInstance and pname:divisor matches the OpenGL
convention (internal issue 1333).
associated material at the top level, vk.xml and associated material in
xml/, and generated include and source files in include/vulkan/ and
src/ext_loader/, respectively (public issue 436).
Jon Leech