Rename client UDF names in the plugin code.

There are number of UDF's which names begin with cal..., e.g. calflushcache. Here is the example how to call it.

MariaDB [test]> select calflushcache();

+-----------------+

| calflushcache() |

+-----------------+

|               0 |

+-----------------+

1 row in set (0.005 sec)

We need to rename the functions replacing cal-prefix with mcs so that calflushcache() becomes mcsflushcache(). However we have to preserve the current cal-prefixed UDFs also to make the transition smooth for customers.
Here is the code where the UDFs' code is and here is the script to define them in MDB.
Plz note there is another group of UDFs defined inside MCS code itself that are prefixed with idb. We don't touch these in the scope of this issue.