Bug Description:
	The page size is retrieved from uint32_t dblayer_page_size.
	Later it is stored in a size_t variable with a cast.
	Depending on little/big endian the page size can be stored in the upper/lower bits of the 64bits variable.
	Later the variable is used to set the page size of a database file using the lower bits (uint32_t) that are zeroed.

Fix Description:
	The BDB callback to set the pagesize, expects a a uint32_t.
	Make sure the field containing it is uint32_t (instead of size_t) as the page
	size is retrieved as a uint32_t as well (dblayer_page_size/BACK_INFO_INDEXPAGESIZE)

https://pagure.io/389-ds-base/issue/49954

Reviewed by: Ludwig Krispen

Platforms tested: F27

Flag Day: no

Doc impact: no