Link with zlib

We will need this for MIRAX 2.2.
Add successful test case for MIRAX 2.2
Add test case for single-level Aperio slide
aperio: Properly map associated images in single-level slides

On single-level Aperio slides, we were dropping the thumbnail and label
and mislabeling the macro image as the thumbnail.  After encountering
exactly one tiled directory, any stripped image would be interpreted as
the thumbnail.  Instead, interpret only the second TIFF directory as the
thumbnail.

Reported-and-debugged-by: Kent Johnson <kent3737@gmail.com>
test/driver: Execute xdelta3 instead of xdelta

On Debian/Ubuntu, /usr/bin/xdelta is xdelta2.
mirax: Read entire slide position file before parsing it

Will be needed for MIRAX 2.2 support.
mirax: Style fixes
mirax: Fix tests
doc: Warn against gratuitous use of openslide_can_open()
mirax: Support for MRXS 2.2

Squashed from pull request #108.
Closes #92, #108.
mirax: Minor MIRAX 2.2 cleanups
mirax: Clean up inflate_buffer() error handling
mirax: Use void * for binary buffers
Add MIRAX StitchingIntensityLayer test cases
README: Add zlib dependency
misc/parse-mirax: Parse StitchingIntensityLayer
misc/parse-mirax: Print all position map records with unusual zz
README: Update requirements
Update for release
Add Aperio 33003 test case