gdb/
	* source.c (symtab_to_fullname): Apply rewrite_source_path also for
	non-existing files.

gdb/testsuite/
	* gdb.mi/mi-fullname-deleted.exp: Set srcfileabssubst and initdir.
	(set substitute-path): New test.
	(fullname present): Remove content.
	(substituted fullname): New test.
gdb/
	* source.c (symtab_to_fullname): Do not prepend DIRNAME for
	non-existing files if FILENAME is already absolute.