Deb: Split libmysqlclient19/20 compat links into a separate package

We already ship libmysqlclient18 that replaces any existing package
with the same name and install symlinks that point to out libmariadb.so.

Instead of creating more packages, we add just one more that does the
same and provides both libmysqlclient19 and -20 replacements symlinks.

This is a clean solution, because systems that only use (and are built
against) libmariadb will not need them and if somebody has done a mistake
in the linker parameters, they will spot it and can easily update the
filename to libmariadb.

debian/control

@@ -50,10 +50,6 @@ Conflicts: mariadb-galera-server-10.0 (<< 10.0.5),
            mariadb-server-5.3,
            mariadb-server-5.5 (<< 5.5.33),
            libmariadbclient18 (<< 10.2.0)
-Replaces: libmysqlclient19,
-          libmysqlclient20
-Provides: libmysqlclient19,
-          libmysqlclient20
 Description: MariaDB database client library
  MariaDB is a fast, stable and true multi-user, multi-threaded SQL database
  server. SQL (Structured Query Language) is the most popular database query
@@ -62,6 +58,25 @@ Description: MariaDB database client library
  .
  This package includes the client library.
 
+Package: libmariadb3-compat
+Architecture: any
+Section: libs
+Depends: mariadb-common, libmariadb3, ${misc:Depends}, ${shlibs:Depends}
+Breaks: libmysqlclient19,
+       libmysqlclient20
+Replaces: libmysqlclient19,
+         libmysqlclient20
+Provides: libmysqlclient19,
+         libmysqlclient20
+Description: MariaDB database client library MySQL compat package
+ MariaDB is a fast, stable and true multi-user, multi-threaded SQL database
+ server. SQL (Structured Query Language) is the most popular database query
+ language in the world. The main goals of MariaDB are speed, robustness and
+ ease of use.
+ .
+ This package includes the client runtime libraries that simulate and replace
+ the equivalents found in MySQL 5.6 and 5.7 (mysqlclient19 and 20).
+
 Package: libmariadbclient18
 Section: libs
 Architecture: any
@@ -74,7 +89,7 @@ Description: Virtual package to satisfy external depends
  language in the world. The main goals of MariaDB are speed, robustness and
  ease of use.
  .
- This package provides compatibility symlinks for libmariadb3
+ This package provides compatibility symlinks for libmariadb3.
 
 Package: libmysqlclient18
 Section: libs
@@ -88,7 +103,7 @@ Description: Virtual package to satisfy external depends
  language in the world. The main goals of MariaDB are speed, robustness and
  ease of use.
  .
- This package provides compatibility symlinks for libmariadb3
+ This package provides compatibility symlinks for libmariadb3.
 
 Package: libmariadb-dev
 Architecture: any

debian/libmariadb3-compat.install

+usr/lib/*/libmysqlclient.so.19
+usr/lib/*/libmysqlclient.so.20

debian/libmariadb3.install

-usr/lib/*/libmysqlclient.so.19
-usr/lib/*/libmysqlclient.so.20
 usr/lib/*/libmariadb.so.*
 usr/lib/mysql/plugin/dialog.so
 usr/lib/mysql/plugin/mysql_clear_password.so