* Bump API patch number and header version number to 28 for this update.
Github Issues:
* Minor spelling and typography cleanup, add definitions of
ename:VK_FALSE and ename:VK_TRUE as just what their names say
(public issues 220, 318, 325, 365; internal issues 451, 496)
* Clarify that the pname:maxDescriptorSet limits in the
<<features-limits-required,Required Limits>> table are n *
maxPerStage limit (where n=number of supported stages) (public issue
254).
* Minor cleanup to <<boilerplate-platform-macros,Platform-Specific
Macro Definitions>> appendix (public issue 314).
* Add valid usage statement to slink:VkPipelineLayoutCreateInfo
disallowing multiple push constant ranges for the same shader stage
(public issue 340).
* Clarify the elink:VkSharingMode description of what executing the
"same" barriers means in case of ownership transfer (public issue
347).
* Rename copyright.txt and add COPYING.md to try and reduce confusion
about applicable copyrights (public issue 350).
* Extend the table in the <<boilerplate-wsi-header, Window System-Specific
Header Control>> section to describe the external headers included when
each etext:VK_USE_PLATFORM_* macro is defined (public issue 376).
Internal Issues:
* Add "Revision History" to the PDF outputs following the table of
contents, to match HTML outputs (internal issue 43).
* Clarified that flink:vkMapMemory may fail due to virtual address
space limitations (internal issue 346).
* Add +refBody+ comment markup for ref page autoextraction when required
(internal issue 400).
* Document proper use of "mipmap" and "mip" in the style guide API
naming rules, matching the spelling rules (internal issue 471).
* Tweak the <<extensions,Layers and Extensions>> appendix to note that
the Specification may be built with arbitrary combinations of
extensions (internal issue 483).
* Remove incorrect statement allowing
slink:VkClearAttachment::pname:colorAttachment to be >=
slink:VkSubpassDescription::pname:colorAttachmentCount (internal
issue 488).
* The <<features-limits-viewportboundsrange,viewportBoundsRange>> is
expressed in terms of the pname:maxViewportDimensions but this is
actually two values. Clarify that it's based on the larger of the two
(if they differ) (internal issue 499).
Other Issues:
* Reflowed text of the entire spec using the 'reflow' Makefile gater,
to (hopefully) reduce future internal git churn as edits are made
and extensions added in return for one-time pain. This has no
perceptible change on the spec outputs but considerable changes on
the asciidoc source (internal issue 367).