Copy over changes from guile.texi.

Copy over changes from guile.texi.

	* python.texi (Basic Python) <gdb.execute>: Add text.
	(Basic Python) <gdb.post_event>: Remove "main" from "main GDB thread".
	(Values From Inferior) <Python string>: Add text.
	(Values From Inferior) <Value.string>: Clarify string length handling.
	(Pretty Printing API): Add cindex.
	(Types In Python) <TYPE_CODE_*>: Use vtable instead of table.
	Remove unnecessary index of gdb.TYPE_CODE_*.  Replace @findex with
	@vindex.
	(Commands In Python) <COMPLETE_*>: Similarly.
	(Symbols In Python) <SYMBOL_*>: Similarly.
	(Breakpoints In Python) <WP_*>: Similarly.
	(Breakpoints In Python) <BP_*>: Similarly.