Move static declarations into C part.
Add support for tonecurve Lr import.
Move colorzones definitions to header file.

This is needed for the lightroom import. At the same time we are
adding two 2 zones from 6 to 8. This gives a better precision and
is at the same time more compatible with what lightroom does and so
will ease the implementation of the import.
Add support for colorzones Lr import.
Rename exposure to blacks.
Add support for exposure Lr import.
Move splittoning definitions to header file.
Add support for splittoning Lr import.
Some people use development versions of glib ...
Merge branch 'po/lr-import'

* po/lr-import:
  Add support for splittoning Lr import.
  Move splittoning definitions to header file.
  Add support for exposure Lr import.
  Rename exposure to blacks.
  Add support for colorzones Lr import.
  Move colorzones definitions to header file.
  Add support for tonecurve Lr import.
  Move static declarations into C part.
Fixed up/down arrow keys in fullscreen preview mode and made left/right arrow keys work the same way. Also implemented the "center scroll" function, which realigns the images with the grid so there is no empty space in front of the first image.
Fixed two bugs concerning keyboard shortcuts for zoomin slider tool in lighttable, which would prevent any images from being shown (offset went outside valid range).