The XDES_CLEAN_BIT is always set for every element of
the page allocation bitmap in the extent descriptor pages.
Do not bother touching it, to avoid redundant writes.
dict_create_index_tree_step(): If the SYS_INDEXES.PAGE does not change,
do not update it in the data dictionary. Typically, all index page numbers
would be unchanged before and after IMPORT TABLESPACE, except if some
secondary indexes were created after loading some data.
btr_root_fseg_adjust_on_import(): Remove the redundant mtr_t* parameter.
Redo logging is disabled during the page adjustments that IMPORT TABLESPACE
is performing.
fsp_alloc_seg_inode_page(): Ever since
commit 3926673ce7149aa223103126b6aeac819b10fab5
all newly allocated pages are zero-initialized.
Assert that this is the case for the FSEG_ID fields.
btr_store_big_rec_extern_fields(): Remove the redundant initialization
of the most significant 32 bits of BTR_EXTERN_LEN. InnoDB never supported
BLOBs that are longer than 4GiB. In fact, dtuple_convert_big_rec()
would write emit an error message if a clustered index record tuple would
exceed 1,000,000,000 bytes in length.
The BTR_EXTERN_LEN in the BLOB pointers in clustered index leaf page
records is zero-initialized at least since
commit 41bb3537ba507799ab0143acd75ccab72192931e
