RFC: cache the CRC in the BFD

[Tom Tromey]

>>>>> "Tom" == Tom Tromey <tromey@redhat.com> writes:

Tom>     	* gdb_bfd.c (struct gdb_bfd_data) <crc_computed, crc>:
Tom>     	New fields.
Tom>     	(get_file_crc): Move from symfile.c.
Tom>     	(gdb_bfd_crc): New function.
Tom>     	* gdb_bfd.h (gdb_bfd_crc): Declare.
Tom>     	* objfiles.h (struct objfile) <crc32, crc32_p>: Remove.
Tom>     	* symfile.c (get_file_crc): Move to gdb_bfd.c.
Tom>     	(separate_debug_file_exists): Use gdb_bfd_crc.

I'm checking this in now.

Tom