* objfiles.h (struct objfile): Add memebers `data' and `num_data'.

* objfiles.h (struct objfile): Add memebers `data' and `num_data'.
(register_objfile_data, set_objfile_data, objfile_data): New
prototypes.
* objfiles.c (objfile_alloc_data, objfile_free_data): New
prototypes.
(allocate_objfile): Call objfile_alloc_data.
(free_objfile): Call objfile_free_data.
(struct objfile_data): New.
(struct objfile_data_registration): New.
(struct objfile_data_registry): New.
(objfile_data_registry): New variable.
(register_objfile_data): New function.
(objfile_alloc_data, objfile_free_data): New functions.
(set_objfile_data, objfile_data): New functions.
* dwarf2-frame.c (dwarf2_frame_data): New variable.
(dwarf2_frame_find_fde, add_fde): Use new per-objfile data mechanism.
(_initialize_dwarf2_frame): New function and prototype.