Move misplaced entries from gdb/ChangeLog to gdb/doc/ChangeLog.

Move misplaced entries from gdb/ChangeLog to gdb/doc/ChangeLog.

2012-08-23  Khoo Yit Phang <khooyp@cs.umd.edu>

	Document how to return from "python-interactive" to GDB.
	* gdb.texinfo (Python Commands): Update documentation.

2012-08-22  Khoo Yit Phang <khooyp@cs.umd.edu>

	Add a new "python-interactive" command that starts a standard
	Python interactive prompt with "pi" as alias, and add "py" as
	an alias to "python".
	* gdb.texinfo (Python Commands): Document the new commands.