Bug 725325 - Drag and drop fails for patterns and brushes

The "drag-data-received" signal was connected wrongly
Bug 725112 - Small canvas doesn't update when zoomed out

Remove all code that tries to calculate the maximum level of the tile
pyramid, because that's essentially impossible. Instead simply keep
track of the max_z encountered in GeglTileSource::command().
Updated Portuguese translation
libgimpcolor: rename our sRGB profile to "GIMP built-in sRGB"
build/win: Upgrade gdk-pixbuf2 to 2.30.6
Bug 725112 - Small canvas doesn't update when zoomed out

gimp_tile_handler_projection_invalidate(): need to invalidate
all levels up to max_z not max_z - 1. Spotted by Massimo.
Bug 725556 - Feather selection extremely slow

gimp_gegl_apply_feather(): add a "dest_rect" parameter to restrict
the feather area. Pass the selection bounds plus the feather radius.

For consistency, newly add gimp_gegl_apply_border,grow,shrink() and use
them in gimpchannel.c