Factor out the i18n definitions into i18n.h include files:
One include file each for libgphoto2 and for libgphoto2_port.
This removes the complete
#ifdef ENABLE_NLS
# include <libintl.h>
# undef _
# define _(String) dgettext (GETTEXT_PACKAGE, String)
# ifdef gettext_noop
# define N_(String) gettext_noop (String)
# else
# define N_(String) (String)
# endif
#else
# define _(String) (String)
# define N_(String) (String)
#endif
block (which in some occasions defines even more macros)
and replaces it with a single line
#include "libgphoto2/i18n.h"
for camlibs and libgphoto2 itself and with
#include "libgphoto2_port/i18n.h"
for iolibs and libgphoto2_port itself.
This gives us two central locations to change the defintions.
0b2b6207c2