dzsave will write a zip file

but see the TODO in dzsave.c

- no way to pick a tile format, always jpeg
- no way to pick a container format, always zip
- needs testing
- examine memuse, how well do we work for large zips
- can we make a zip over 4gb?
Merge remote-tracking branch 'origin/master' into dzsave-gsf

Conflicts:
	ChangeLog
use vips_foreign_save_buffer()

so dzsave now knows about save options
add @container option to dzsave
Merge branch 'master' into dzsave-gsf
Merge branch 'master' into dzsave-gsf
oops fix non-zip output
Merge branch 'dzsave-gsf' of github.com:jcupitt/libvips into dzsave-gsf
sync
Merge branch 'master' into dzsave-gsf

Conflicts:
	ChangeLog
better gcc detect
sort out dzsave paths, auto-enable zip

rationalised output paths for dzsave

enable zip automatically if output name ends in .zip
TODO notes
update dzsave docs
safer vips_operation_new()

fixes "$ vips vips" segv
move some junk to deprecated/
Merge branch 'dzsave-gsf'

Conflicts:
	libvips/include/vips/vips.h
Merge branch 'dzsave-gsf'
oops, don't treat RGB16 as sRGB in colourspace

we still had code to treat RGB16 inputs as sRGB even though we now have
a special set of RGB16 paths

vips copy 16bitRGB.tif x.jpg

now works
set Type on memory strip

we need to set Type on memory strips so we can convert to the output
format correctly, thanks philipgiuliani

see https://github.com/jcupitt/libvips/issues/120