[autofit] Move declaration of writing systems into separate file. This has the benefit that we don't need to duplicate the data at different places. * src/autofit/afwrtsys.h: New file. * src/autofit/aftypes.h (AF_WritingSystem): Include `afwrtsys.h' to define the enumeration values. * src/autofit/afglobal.c: Include `afwrtsys.h' to get the writing system specific header files. Include `afpic.h'. (af_writing_system_classes): Include `afwrtsys.h' to fill this array. * src/autofit/afpic.c: Include `afwrtsys.h' to get the writing system specific header files. (autofit_module_class_pic_init): Include `afwrtsys.h' for initialization. * src/autofit/afpic.h (AF_WRITING_SYSTEM_CLASSES_COUNT, AF_WRITING_SYSTEM_CLASSES_REC_COUNT): Removed. Use `AF_WRITING_SYSTEM_MAX' instead.