publish cl_khr_external_memory_android_hardware_buffer

[bashbaug]

Publish the cl_khr_external_memory_android_hardware_buffer extension (experimental).

[bashbaug]

Here are a few comments and questions I found while editing this specification.

[bashbaug]

I ended up completely refactoring the error conditions for clCreateBufferWithProperties and clCreateImageWithProperties as part of this PR, following the guideance from #1320. This makes for bigger diffs, but I think the end result is much more readable. Please take a look.

[bashbaug]

Here are two minor issues I found while refactoring the error conditions for clCreateImageWithProperties.

[bashbaug]

I have a few additional questions about this error code:

1. Elsewhere in this PR we say for the AHardwareBuffer case: "If importing as a buffer, the implementation will infer the size of the buffer." What does this mean for the passed-in size? Specifically, what happens if the passed-in size is smaller than the size of the AHardwareBuffer? Does the inferred size replace the passed-in size?
2. In the AHardwareBuffer case is a size of zero valid? Note that this is a CL_INVALID_BUFFER_SIZE error in general (without AHardwareBuffer), so we would need to explicitly allow this if a size of zero is valid.

[joselopeqti]

We agree that for the AHardwareBuffer the passed-in size should be always zero and the buffer size inferred, so we should remove the CL_INVALID_BUFFER_SIZE error for this case

[bashbaug]

Great. I think I have clarified this now - please take a look.

[joselopeqti]

Yeah, I think now it is good. The sample code of the extension should also be changed as the size is still being passed to clCreateBufferWithProperties

[bashbaug]

Thanks, I fixed the one example code snip I found. Please take a look - is this the only one? dbe13e7

[bashbaug]

Merging as discussed in the July 1st teleconference.