In demo code, demonstrate zero-copy memory alignment

[shusheer]

For many GPUs (IoT devices using unified memory models, Intel iGPUs, and GPUs with pinned memory), zero-copy buffers are really useful. You use malloc() in the examples currently, which only aligns to 8-byte boundaries typically. Intel requires 4096-byte boundaries, ARM usually requires 64-bytes, etc. Unfortunately Windows uses different alignment methods than Linux, but this stackoverflow question gives a nice example of how to #ifdef wrap a mimic of posix_memalign : https://stackoverflow.com/a/33696858 and https://stackoverflow.com/a/38291021

To make life easy for people you could create a function that extracts CL_DEVICE_MEM_BASE_ADDR_ALIGN and uses this to correctly align buffers (and have a corresponding free call, to abstract windows/linux differences).