* libxbps: improved xbps_get_file_hash() to mmap(2) rather than read(2)
the file we have to process. With mmap'ed files the hash can be
processed 5x faster than before, or even more in some cases.
* libxbps: switch to OpenSSL SHA256 implementation and remove the one
previously used. It's faster and OpenSSL is required for libfetch so
there is not point in using it.
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