we had both a class member bandjoin, and an instance member
Vips.Image.bandjoin([i1, i2, i3..])
i1.ibandjoin([i2, i3..])
this was confusing and annoying ... get rid of the class one and just
use bandjoin everywhere, so this is now the way to do it:
i1.bandjoin([i2, i3..])
There was a mixup with the previous fix to dzsave overlap handling,
correct it and update the test suite.
In the previous revision, dzsave overlapped tiles by overlap and sized
them by tile_size. In fact, tiles should be sized as (tile_size + overlap
* 2), ie. tile_size refers to the number of unique pixels per tile.
See https://github.com/jcupitt/libvips/issues/357
oh argh class and instance methods are in the same namespace, so we have
to rename the instance one as ibandjoin
also, start adding a test for arrayjoin
we were adding up to two bytes of null to the end of base64-encoded
binary data due to a signed/unsigned mixup
add a test for this, plus a test for vips file format
