tinf.h: TINF_DATA is now part of external API.

Users need to have freedom where and how to allocate it.
tinflate, tinfzlib: Provide API taking TINF_DATA* and incremental alloc.

The new API takes a pointer to TINF_DATA (which thus can be allocated by
caller the way it sees fit) and provides callback to incrementally increase
size of decompression buffer.