static (hidden) methods to the castor/log/Log.cpp file:

    castor_openlog()
    castor_closelog()
    castor_syslog()

These three methods are copies of the dlf_openlog(), dlf_closelog() and
dlf_syslog() functions defined in the file CASTOR/dlf/dlf_lib.c.  I have
renamed the associated static global variables using the "s_" naming convention.

Please note that this commit does not finish the implementation of the new
logging API (I here a groan from the back).  Again I'm looking for feedback
(again another groan from the back).