For both Deb and RPM, create mariadb-client-compat and
mariadb-server-compat containing the mysql links to the mariadb
named executables/scripts.
The mariadb-client-core mysqlcheck was moved to mariadb-client-compat.
The symlinks in MYSQL_ADD_EXECUTABLE is tagged as a
{Client,Server}Symlinks component and placed in
the symlinks packages.
Man pages are restructured be installed into compat package
if that matches the executable.
Columnstore has a workaround as it doesn't use the cmake/plugin.cmake.
Scripts likewise have compatibility symlinks are in
the {server,client}-compat packages.
Co-author: Andrew Hutchings <andrew@linuxjedi.co.uk>
Closes#2390
