glave: move code-gen'ed files.
glave: move code-gen'ed files.

* glave-generate.py has moved into tools/glave/scripts/ and renamed to vk-generate.py
* all code-gen'ed files now live in the source tree
* all code-gen'ed files are now generated into a "codegen" directory local to the project to make it easier to spot when a generated file has changed or is being debugged.
* all code-gen'ed files are now being checked in so that we can better track differences caused by the code-gen as the header file evolves.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools