The functions MY_CHARSET_HANDLER::caseup() and MY_CHARSET_HANDLER::casedn()
in their virtual imlementations do "const char *end= src + srclen"
in the very beginning. Therefore src cannot be NULL to avoid
"UBSAN: SUMMARY: UndefinedBehaviorSanitizer: nullptr-with-offset".
Adding DBUG_ASSERT(src != NULL) into all virtual implementations,
to catch this problem in regular Debug builds (without UBSAN).
Fixing Master_info_index::get_master_info() to check connection_name->str.
If it is NULL then passing empty_clex_str into IdentBufferCasedn
instead of *connection_name.
Make the slave options --replicate-* dynamic variables so that these
options can be changed dynamically while the server is running,
which enables users to modify replication filtering rules without
having to stop and restart the server.
This is accomplished by just requiring that the slave threads are
stopped when these options are set dynamically. Since filtering
rules are only used by the SQL slave thread, setting them while the
thread is not running avoids the need for locking.
