Merge remote-tracking branch 'origin/7.40'
fix vipsthumbnail on very-many-core systems

see:

https://github.com/jcupitt/libvips/issues/160

we were using UNBUFFERED, but on very-many-core systems this can get out
of order enough to make vipspng free the read object early
enlarge the buffered tilecache

helps vipsthumbnail under load
fix matlab load

oops, width and height were swapped
fix memleak in tilecache
fix memleak in type.c

see

https://github.com/jcupitt/libvips/pull/164
Merge branch 'master' of github.com:jcupitt/libvips
Merge branch '7.40'

Conflicts:
	ChangeLog
	configure.ac