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
safer vips_operation_new()

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

Conflicts:
	libvips/include/vips/vips.h