gdb/doc/

gdb/doc/
	* gdb.texinfo (Data): New @menu reference to Pretty Printing.
	(Python API): Change the reference to Pretty Printing API.
	(Pretty Printing): Move the user part under the Data node.  Reformat
	the sample output to 72 columns.  Create a new reference to Pretty
	Printing API.  Rename the API part ...
	(Pretty Printing API): To a new node name.
	(Selecting Pretty-Printers, Progspaces In Python, Objfiles In Python)
	(GDB/MI Variable Objects): Change references to Pretty Printing API.