lock on area tracking
better type leak checks
don't output transparency ifrom openslide

openslide now always outputs solid colours, helps vips_flatten() convert
to RGB for jpg tile save correctly
oops
Merge remote-tracking branch 'origin/master'
Merge remote-tracking branch 'origin/7.34'

Conflicts:
	libvips/iofuncs/type.c
Merge remote-tracking branch 'origin/master' into webp
basic webp load done
added webpsave boilerplate