* symmisc.c (print_symbol_bcache_statistics): Print filename cache

	* symmisc.c (print_symbol_bcache_statistics): Print filename cache
	statistics.
	(print_objfile_statistics): Likewise.
	* symfile.c (reread_symbols): Initialize filename_cache.
	(allocate_symtab): Cache the file name.
	(allocate_psymtab): Likewise.
	* solib-sunos.c (allocate_rt_common_objfile): Initialize
	filename_cache.
	* objfiles.h (struct objfile) <filename_cache>: New field.
	* objfiles.c (allocate_objfile): Initialize filename_cache.
	(free_objfile): Free filename_cache.