new tablespaces created from now on.

btr_store_big_rec_extern_fields(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_BLOB.

buf_page_print(): Decode FIL_PAGE_TYPE.  Replace if-else with switch().

buf_page_create(): Set FIL_PAGE_PREV, FIL_PAGE_NEXT and FIL_PAGE_TYPE.

trx_sysf_create(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_TRX_SYS.
Initialize TRX_SYS_RSEG_SPACE.

FIL_PAGE_TYPE: Document that the field cannot be relied on in older
versions of MySQL/InnoDB.  Add new type codes.

ibuf_bitmap_page_init(): Document that the rest of the page is uninitialized.

ibuf_add_free_page(): Log the setting of FIL_PAGE_TYPE.

fsp_header_init(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_FSP_HDR.
Initialize FSP_NOT_USED.

fsp_fill_free_list(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_XDES.

fsp_alloc_seg_inode_page(): Set FIL_PAGE_TYPE to FIL_PAGE_INODE.

fseg_create_general(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_SYS.