This is a list of servers, separated by commas. When queried as a
config setting, returns a null-terminated array of SERVER*:s. The
commit includes a serverlist parsing function, which should probably
be used anywhere a similarly formed string is parsed.
Moved some typedefs to router.h and server.h, changed a few
constants to these enums. Renamed some types in config.h to
remove "Gateway".
There are still some functions in the public header which are
only used in core, but they seem to fit the theme of public functions
so were not moved.
The external config.h header defined functions and structures that are
intended to be used by modules. The internal header contains functions
that are used only by the MaxScale core.
