John Cupitt ad56c57830 add implementation for VImage::write()
oops, it was missing

also, change the return type from void to VImage. This makes chaining
possible, eg.:

   VImage memory = im.write( Viameg::new_memory() );
2016-06-10 14:22:08 +01:00
..
2014-10-20 11:50:34 +01:00