* Bump API patch number and header version number to 67 for this update.
* Update copyright dates to 2018
Github Issues:
* Fix texture lookup functions in `GL_KHR_vulkan_glsl` specification
(public pull request 363).
* Clarify the state waited semaphores are left in when a call to
flink:vkQueuePresentKHR fails (public issue 572).
* Cleanup descriptions of slink:VkObjectTablePushConstantEntryNVX and
slink:VkObjectTableDescriptorSetEntryNVX (public issue 583)
* Remove redundant flink:vkCmdSetDiscardRectangleEXT valid usage
statements (public pull 586).
* Make dynamic state array length valid usage statements implicit for
flink:vkCmdSetViewportWScalingNV, flink:vkCmdSetDiscardRectangleEXT, and
flink:vkCmdSetViewport (public pull 589).
* Clarify meaning of window extent (0,0) in slink:VkSwapchainKHR for the
Windows and X11 platforms, in their respective extensions (public issue
590).
* Allow flink:vkGetPastPresentationTimingGOOGLE to return
ename:VK_INCOMPLETE (public issue 604).
* Add synchronization valid usage statements to flink:vkAcquireNextImage
(public pull 611).
* Fix some broken external links and internal xrefs (public pull 613).
* Clean up slink:VkViewport valid usage statements in the presence or
absence of relevant extensions (public pull 623).
* Remove
ename:VK_IMAGE_LAYOUT_DEPTH_READ_ONLY_STENCIL_ATTACHMENT_OPTIMAL_KHR
token from VK_KHR_maintenance2 from the non-extension VU path for
slink:VkGraphicsPipelineCreateInfo (public issue 628).
* Miscellaneous minor markup fixes - extension name strings (public pull
631), Notes (pull 633), queue names emitted by generator scripts (pull
634), block formatting in slink:VkDescriptorUpdateTemplateEntryKHR (pull
635), ename:VK_FORMAT_FEATURE_SAMPLED_IMAGE_FILTER_CUBIC_BIT_IMG (pull
641), quotes and apostrophes (pull 643),
* Miscellaneous minor grammar fixes (public pull 644).
* Fix markup macros so usage like ptext:*Src* works (public pull 647).
Internal Issues:
* Clarify in the `VK_KHR_surface` and `VK_KHR_swapchain` extensions that
parameter combinations which aren't supported for normal images are also
unsupported for presentable images, even if the parameter values are
individually supported as reported by the surface capability queries
(internal issue 1029).
* Fixed XML typo in the valid value field of the pname:sType member of
slink:VkPhysicalDeviceExternalMemoryHostPropertiesEXT (internal issue
1100).
Other Issues:
* Add memory semantics validity rules to the <<spirvenv-module-validation,
Validation Rules within a Module>> section of the SPIR-V environment
appendix, and specify that sequentiality consistency is not supported.
This forbids certain cases like "`Load+Release`" that we don't expect to
ever be meaningful.
* Document mapping of OpenGL Shading Language barriers to SPIR-V scope and
semantics in the `GL_KHR_vulkan_glsl` specification.
New Extensions:
* `VK_EXT_conservative_rasterization`
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