Centralize printing "<optimized out>".

	Centralize printing "<optimized out>".

	gdb/
	* valprint.h (val_print_optimized_out): Declare.
	* cp-valprint.c (cp_print_value_fields): Use
	val_print_optimized_out.
	* jv-valprint.c (java_print_value_fields): Ditto.
	* p-valprint.c (pascal_object_print_value_fields): Ditto.
	* printcmd.c (print_formatted): Ditto.
	* valprint.c (valprint_check_validity): Ditto.
	(value_check_printable): Ditto.
	(val_print_optimized_out): New.

	gdb/doc/
	* gdb.texinfo: s/value optimized out/optimized out/g

	gdb/testsuite/
	* gdb.base/frame-args.exp: Adjust.
	* gdb.dwarf2/dw2-noloc.exp: Adjust.
	* gdb.dwarf2/dw2-inline-param.exp: Adjust.
	* gdb.dwarf2/pieces.exp: Adjust.
	* gdb.opt/clobbered-registers-O2.exp: Adjust.
	* gdb.opt/inline-locals.exp: Adjust.
	* gdb.threads/fork-child-threads.exp: Adjust.