gdb/

gdb/
	Add a new variable that controls a way in which filenames are
	displayed.
	* NEWS (set filename-display): New entry.
	* source.c (filename_display_basename, filename_display_relative)
	(filename_display_absolute, filename_display_kind_names)
	(filename_display_string, show_filename_display_string)
	(symtab_to_filename_for_display): New.
	(_initialize_source): Added initialization of 'filename-display'
	variable.
	* source.h (symtab_to_filename_for_display): Added declaration.
	* stack.c (print_frame): Added new variable and calling of a new
	function and condition with this variable. Changed third argument of
	calling of a function.

gdb/doc/
	* gdb.texinfo (Backtrace): Added description of 'filename-display'
	variable in 'set/show backtrace' section.

gdb/testsuite/
	* gdb.dwarf2/dw2-dir-file-name.exp: New file.
	* gdb.dwarf2/dw2-dir-file-name.c: New file.