Change: forcefully enable prefixing logs with date (#11930)

Additionally, add the log-level to the log message.

Fix #11646: Non-thread safe shared buffer returned from GetLogPrefix().

Return string from GetLogPrefix instead of shared string's buffer.

Codechange: minor bits and pieces related to fmt::format() (#11806)

- Don't make run-time formatting what can be done compile-time.
- Be explicit about run-time formatting.
- Fix datetime printing.

Remove: Debug redirect over network

It does not work for dedicated servers because upon starting the process to
resolve the address to redirect to gets killed. Also with all the async going
on in the network code, the debug redirection will start very late in the
process.

Change: Rename some freetype things to fontcache.

The font cache supports more than just FreeType as a font provider, but still used freetype in some naming.

This now uses more suitable terms.

Codechange: use thread safe time functions

Functions like localtime, gmtime and asctime are not thread safe as they (might) reuse the same buffer. So use the safer _s/_r variant for localtime and gmtime, and use strftime in favour of asctime.

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.

Remove: NO_DEBUG_MESSAGES was only read and setting it broke compilation (#6703)

Given any speed issue cannot be attributed to checking for _debug_NNN_level, removing this is a safe action

This fixes #6652.

(svn r16269) -Codechange: use gcc's ability to check parameters sent to printf-like functions
-Fix: wrong number of parameters or wrong parameter types sent to printf-like functions at several places

(svn r10778) -Fix: one-liners to allow MSVC and WINCE to work together (or anyway, a step towards that goal)
-Fix: put DEBUG lines under WINCE via a function designed for just that under WINCE

(svn r8862) -Cleanup: doxygen changes, again. Mostly @files missing tags and a few comments style.
Some documentation addition, when i can easily supply them

(svn r8631) -Add: added parameter -l ip[:port] to ./openttd, which redirects DEBUG() to a remote connection over TCP
For example, launch on 192.168.0.1 with, say, netcat a listener: netcat -l -p 3982
Launch OpenTTD on a remote host (say, PSP): ./openttd -l 192.168.0.1 -d9
And you get all debug information on 192.168.0.1. Very useful for debugging Portable systems.