Also implements the feature request in:
Bug#58819 preload InnoDB buffer pool option
BUG 11765816 - 58819: PRELOAD INNODB BUFFER POOL OPTION

This feature implements the possibility to dump and restore the contents
of the InnoDB buffer pool(s) to/from disk. The main objective is to
shorten the warm up times after the server has been restarted by loading
the data that has been loaded before shutdown.

This feature consists of two parts:

== 1. Dumping the buffer pool or part of it on disk. Only tablespace id
   and page id are saved. Pages content is not saved.

== 2. Loading the pages listed in a dump into the buffer pool.

Reviewed by:	Inaam Rana (rb://661)
Tested by:	Michael Izioumtchenko, Vasil Dimov and PB2