tiny polish
single-thread class init

See:

  https://github.com/jcupitt/libvips/issues/64

We were seeing races in class init on very-many-core machines. GObject
is supposed to single-thread class init, I think, so this shouldn't
happen. Perhaps class init via g_type_class_ref() is not
single-threaded.
fix ushort save with values >32k

we were not setting the fits offset correctly for ushort images, thanks
weaverwb
missing include
ping all classes in dzsave

fixes a race in class build on many-core machines, see

https://github.com/jcupitt/libvips/issues/64
remove the class init lock

the previous patch was not sufficient, remove it
whitespace
TODO note
fix morph on non-uchar images
fix two trivial compiler warnings
Merge remote-tracking branch 'origin/7.34' into 7.34
strip ICC profile on conversion in xyz2srgb

if we use the vips xys->srgb  path (ie. not the lcms one) we must remove
any ICC profile left over from import, otherwise we may have srgb pixels
with a non-srgb profile