Back in 2006 or 2007, when MySQL AB and Innobase Oy existed as
separately controlled entities (Innobase had been acquired by
Oracle Corporation), MySQL 5.1 introduced a storage engine plugin
interface and Oracle made use of it by distributing a separate
InnoDB Plugin, which would contain some more bug fixes and
improvements, compared to the version of InnoDB that was statically
linked with the mysqld server that was distributed by MySQL AB.
The built-in InnoDB would export global symbols, which would clash
with the symbols of the dynamic InnoDB Plugin (which was supposed
to override the built-in one when present).

The solution to this problem was to declare all global symbols with
UNIV_INTERN, so that they would get the GCC function attribute that
specifies hidden visibility.

Later, in MariaDB Server, something based on Percona XtraDB (a fork of
MySQL InnoDB) became the statically linked implementation, and something
closer to MySQL InnoDB was available as a dynamic plugin. Starting with
version 10.2, MariaDB Server includes only one InnoDB implementation,
and hence any reason to have the UNIV_INTERN definition was lost.

btr_get_size_and_reserved(): Move to the same compilation unit with
the only caller.

innodb_set_buf_pool_size(): Remove. Modify innobase_buffer_pool_size
directly.

fil_crypt_calculate_checksum(): Merge to the only caller.

ha_innobase::innobase_reset_autoinc(): Merge to the only caller.

thd_query_start_micro(): Remove. Call thd_start_utime() directly.