kes Implement DB Driver = string for the DBI driver.

kes  Implement DB Driver = string for the DBI driver.
kes  Remove all old bdb_xxx.c code.  Add dummy routines to bdb.c
kes  First cut of code for loading Win32 plugin dlls. Implement
     dlopen, dlsym, dlclose, and dlerror in src/win32/compat/compat.cpp
     and implement a dlfcn.h file based on opengroup's definitions of
     the functions.

git-svn-id: https://bacula.svn.sourceforge.net/svnroot/bacula/trunk@6358 91ce42f0-d328-0410-95d8-f526ca767f89