Generally replace use of @available() with respondsToSelector:.
Add mvkMakeOSVersion() and mvkOSVersionIsAtLeast(macos,ios) to help testing OS versions.
Set maxDrawIndexedIndexValue to kMVKUndefinedLargeUInt32 instead of uint32_t max.
Use MVK_CONFIG_AUTO_GPU_CAPTURE_OUTPUT_FILE to set the destination file.
This is useful for capturing traces where the program in question cannot
be run under Xcode's control; the captured trace can then be inspected
later with Xcode.
This new feature requires Metal 3.0 (macOS 10.15, iOS 13).
This is the heap representing system memory. The memory type
corresponding to `MTLStorageModeShared` is reported as belonging to this
heap.
I've tried to correct the reported size of the heaps as well while I'm
at it. UMA GPUs and the system heap for NUMA GPUs use the system memory
size as the heap size, and the amount of available memory as the budget.
iOS 13 uses the new `os_proc_available_memory()` API for this purpose.
NUMA GPUs additionally use the memory used by the process as a crude
measure of system heap usage.
