Make libmariadb-dev conflict/replace libmysqlclient-dev (Closes: #863675)

This mimics how libmariadbclient-dev used to conflict/replace the same
libmysqlclient-dev and libmysqld-dev packages. These packages are not
supposed to be co-installable anyway.

Among others, the following files conflict:
- /usr/bin/mysql_config
- libmysqlservices.a
- mysql.m4

Also, wrap-and-sort -a in this commit.