We might reintroduce it later, but for now remove, as it was unused.
Some things that should have been in this object (drop_hints, etc)
are already in hb_subset_input_t. So, for now, keep everything there.
* [subset] sanitize individual DeviceRecord's as part of hdmx sanitization.
* [subset] Fix out of bounds read with non-two byte align glyphs.
* [subset] Just use size_device_record >= DeviceRecord::min_size.
* [subset] Add TODO.
* [subset] Re-order checks in hdmx sanitize.
Include stdbool.h in hb-setset-test.h instead of in the individual
sources, if it is found; otherwise use a simplistic fallback for it if
it is not found.
Also declare variables at the top of the block, to build on pre-C99
compiliers.
