[Libreoffice] Updating external to new version: mysqlcppconn

I have in my local working dir an upgrade of the bundled mysqlcppconn
to latest "officially stable" version; it was my first shot at
fdo#42865.

Since I've done the work, I can as well push it; mysqlcppconn's
changelog (bugs fixed) suggests to me it is a good idea.

1) I wanted to first check whether we have a specific policy on when /
   how / why we upgrade bundled externals to newer versions, and if
   that policy tells I should not do it in the current situation.

2) The tarball downloaded from mysql.com unpacks into
   mysql-connector-c++-1.1.0, not mysql-connector-cpp. Am I supposed
   to "repackage" the tarball so that it unpacks into
   mysql-connector-cpp or to change makefile.mk to adapt to the new
   name? (FYI, in my local copy, I have changed makefile.mk to adapt
   to the new name.)

3) I'm also removing from the patch the hunks that do

   // hack around the non-existent ::boost::variant in OOo 3.1 build env

   Since it has been in boost since 2002/2003, so our baseline
   "minimal version supported" of boost should have it!

   Our bundled boost (version 1.44) has boost::variant.

-- 
Lionel