RFC: add libdeflate to SuperBuild

The GDAL 3.2.0 release notes mention:

  • Add optional libdeflate dependency for faster Deflate compression/decompression

This is the last test case from #2136 (closed):

Format Size Compression time Compression time (MT) Decompression time
Uncompressed 241 187 444 b N/A N/A N/A
DEFLATE (GDAL 3.2.0) 159 937 804 b 2.053s 0.392s 1.722s
DEFLATE (GDAL 3.1.0) 159 740 861 b 6.638s 0.572s 1.311s

There's a huge improvement in DEFLATE performance in 3.2.0.

This might need adding a new library (libdeflate) to SuperBuild and also upgrading libtiff.

Edited by Laurențiu Nicola