* Bump API patch number and header version number to 49 for this update.
Github Issues:
* Modify reference page extraction script to make internal links to spec
anchors refer to the core specification instead of being dangling links
(public issue 455).
* Fix GL_KHR_vulkan_glsl typo and add a nor-normative mapping to the newly
published StorageBuffer class (public issue 466).
* Both flink:vkEnumerateInstanceExtensionProperties and
flink:vkEnumerateDeviceExtensionProperties return
ename:VK_ERROR_LAYER_NOT_PRESENT, which covers the error case of an
application providing a layer name that wasn't returned by
ftext:vkEnumerate{Instance|Device}LayerProperties (public issue 487).
* The specification for flink:VkApplicationInfo::apiVersion says that the
driver must return ename:VK_ERROR_INCOMPATIBLE_DRIVER in the case that
pname:apiVersion specifies a non-supported version. That means that the
valid usage should not also state that, and so the VU statement is
removed. The VU had language about "`an effective substitute`" that
would have been lost, and so it was moved to the pname:apiVersion
description (public issue 488).
Internal Issues:
* Modify implicit validity generator script to assign asciidoc anchors to
all valid usage statements it generates, and reflow.py script to insert
Valid Usage ID (VUID) tags into the specification source files for
explicit valid usage statements. This has no semantic effects on the
specification, but will support the validation layer's detection of
valid usage violations and allow it to link into the corresponding part
of the specification (internal issue 583).
* Assign VUID tags to all explicit VU statements and document
the process and tag format in the style guide (internal issue 583).
* Clarify the rules of whether to structure new functionality as instance
extensions, device extensions, or both in the
<<extended-functionality-instance-extensions-and-devices, Instance
Extensions and Device Extensions>> section (internal issue 749).
* Require that SPIR-V run-time arrays are only used with the
code:BufferBlock decoration (internal issue 750).
* Fix implicit and explicit valid usage statements for
slink:VkWriteDescriptorSet::pname:dstSet (internal issue 767)
* Fix SPIR-V code sample for ename:VK_DESCRIPTOR_TYPE_UNIFORM_TEXEL_BUFFER
in the <<descriptorsets-uniformtexelbuffer, Uniform Texel Buffer>>
section (internal issue 770).
* Clarify that disabling depth testing also disables depth writes in the
<<fragops-ds-state, Depth and Stencil Operations>> section (internal
issue 775).
* flink:VkDescriptorImageInfo::pname:imageLayout must match the actual
imageLayout at the time the image is accessed. This was in the spec
text, but needed an associated valid usage statement.
* Note that only 32-bit atomic operations are supported in the
<<spirvenv-module-validation, Validation Rules within a Module>>
section.
* Note that code:UniformConstant variables must not have initializers in
the <<spirvenv-module-validation, Validation Rules within a Module>>
section.
* Add a new elink:VkObjectType enumeration to the core API, promoted from
elink:VkDebugObjectTypeEXT, since it is used for much more than just the
debug_report extension.
New Extensions:
* `VK_KHR_get_surface_capabilities2`
* `VK_KHR_shared_presentable_image`
Jon Leech