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.
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.