ut_align_down(): Preserve the const qualifier. Use C++ casts.

ha_delete_hash_node(): Correct an assertion expression.

fil_page_get_type(): Perform an assumed-aligned read.

page_align(): Preserve the const qualifier. Assume (some) alignment.

page_get_max_trx_id(): Check the index page type.

page_header_get_field(): Perform an assumed-aligned read.

page_get_autoinc(): Perform an assumed-aligned read.

page_dir_get_nth_slot(): Perform an assumed-aligned read.
Preserve the const qualifier.