(svn r6754) -Codechange: Remove some #idef ENABLE_NETWORK specific defines. With networking
disabled hardcode _networking/_network_available to zero and let the compiler
handle all optimizations.

(svn r2962) - const correctness for all Get* functions and most Draw* functions that don't change their pointer parameters
- change a lot of byte player types to PlayerID
- beautify header files, same "#endif /* filename */" ending

(svn r1240) -Fix: OpenTTD once again compiles if ENABLE_NETWORK is disabled.
-Fix: removed some warnings
-Enabled ENABLE_NETWORK on windows again which I accidentally commented out.

(svn r1228) -Add: [Network] When a server normally shuts down, it removed itself
from the server-list

(svn r1227) -Add: Ingame Server-list (select Internet, then Find Servers)
-Fix: UDPListener was launched wrongly
-Fix: Not all sockets have broadcast enabled anymore
-Fix: Server-advertise retries 3 times before giving up

(svn r1168) -Cleanup: [Network] Cleaned the network code a bit. Added 'const'
and 'void' where needed, prefixed all functions, typedefs and global
vars with 'Network' and organized all externals nicely.

(svn r1106) -Add: [Network] Added master-server protocol and advertise to
master-server option. No GUI yet, and disabled by default (it still is WIP)