From Lorenzo:

- only use external GSL for mathmore.
From le:
- by default build now: mathcore, mathmore, reglex and cintex.
- check for mysql version >= 3.23.x after changes by Sergei.


git-svn-id: http://root.cern.ch/svn/root/trunk@15553 27541ba8-7e3a-0410-8455-c3a389f83636