Predefined items and tags

These are the items defined in the hw/sysinfo.h file. Note that you're free to create additional items — these are just what we needed for our own purposes. You'll notice that all things are defined as HWI_TAG_NAME_*, HWI_TAG_ALIGN_*, and struct hwi_*. The names are chosen that way so that the HWI_TAG_INFO() macro in startup works properly.