* xcoffread.c (read_xcoff_symtab): Make `debugfmt' const.

	* xcoffread.c (read_xcoff_symtab): Make `debugfmt' const.
	* symtab.h (struct symtab) <producer, debugformat>: Now const.
	* symmisc.c (free_symtab): Don't free debugformat.
	* buildsym.h (struct subfile) <producer, debugformat>: Now const.
	(record_debugformat, record_producer): Document.
	* buildsym.c (end_symtab): Don't save debugformat and producer
	names on obstack.
	(end_symtab): Don't free debugformat and producer fields.
	(record_debugformat): Don't call xstrdup.
	(record_producer): Likewise.