Remove: "language" field from server/client

The original idea was that people could find a server they could
talk in their native language on. This isn't really used in that
way. There are several reasons for removing this:

- the client also sends his "language" to the server, but nothing
is doing anything with this.
- flags are a bad way to represent languages, and over the years
we had several (rightfully) complaints about this.
- most servers have their language set to "All", and prefix the
servername with the language it is about. This is a much more
efficient way to do the same.

All in all, this feature should go back to the drawing board.
Maybe it could work in another form, but this form is not it.

Remove: "map_name" from server announcements / listing

The idea back in the days was nice, but it never resulted in
anything useful. Most servers either read "(loaded game)" or
"Random Map", neither being useful. It was meant for heightmaps,
so you could find a server that was using a specific one .. but
there are many things wrong with that idea. Mostly, servers tend
to save and load savegames from time to time, after which the
original heightmap used was lost.

All in all, removing map_name all together is just better.

Remove: ENABLE_NETWORK switch

This switch has been a pain for years. Often disabling broke
compilation, as no developer compiles OpenTTD without, neither do
any of our official binaries.

Additionaly, it has grown so hugely in our codebase, that it
clearly shows that the current solution was a poor one. 350+
instances of "#ifdef ENABLE_NETWORK" were in the code, of which
only ~30 in the networking code itself. The rest were all around
the code to do the right thing, from GUI to NewGRF.

A more proper solution would be to stub all the functions, and
make sure the rest of the code can simply assume network is
available. This was also partially done, and most variables were
correct if networking was disabled. Despite that, often the #ifdefs
were still used.

With the recent removal of DOS, there is also no platform anymore
which we support where networking isn't working out-of-the-box.

All in all, it is time to remove the ENABLE_NETWORK switch. No
replacement is planned, but if you feel we really need this option,
we welcome any Pull Request which implements this in a way that
doesn't crawl through the code like this diff shows we used to.

(svn r13369) -Codechange: remove duplication of network configuration settings between NetworkSettings and NetworkGameInfo.
-Fix: failure of changing the server password during games because the password wasn't duplicated properly.

(svn r8361) -Codechange: make sure the range of the dates coming from the network are valid in OpenTTD
-Codechange: use_password is a boolean variable
-Codechange: move range checking for server_lang and map_set to Recv_NetworkGameInfo

(svn r7759) -Merge: makefile rewrite. This merge features:
- A proper ./configure, so everything needs to be configured only once, not for every make.
- Usage of makedepend when available. This greatly reduces the time needed for generating the dependencies.
- A generator for all project files. There is a single file with sources, which is used to generate Makefiles and the project files for MSVC.
- Proper support for OSX universal binaries.
- Object files for non-MSVC compiles are also placed in separate directories, making is faster to switch between debug and release compiles and it does not touch the directory with the source files.
- Functionality to make a bundle of all needed files for for example a nightly or distribution of a binary with all needed GRFs and language files.

Note: as this merge moves almost all files, it is recommended to make a backup of your working copy before updating your working copy.