This adds a chat console the server owner can use for administration
or to talk with players.
It runs in its own thread, which makes the user interface immune to
the server's lag, behaving just like a client, except timeout.
As it uses the same console code as the f10 console, things like nick
completion or a scroll buffer basically come for free.
The terminal itself is written in a general way so that adding a
client version later on is just about implementing an interface.

Fatal errors are printed after the console exists and the ncurses
terminal buffer gets cleaned up with endwin(), so that the error still
remains visible.

The server owner can chose their username their entered text will
have in chat and where players can send PMs to.
Once the username is secured with a password to prevent anybody to
take over the server, the owner can execute admin tasks over the
console.

This change includes a contribution by @kahrl who has improved ncurses
library detection.

Fix memory leak in minetest.place_schematic
Slightly refactor Schematic code

Use type 'string' for v3fs and add comments

Before, time progressed wrongly. This was due to a mistake in how m_time_of_day_f was calculated,
and a regression of the last two commits.

The Atomic implementation was only partially correct, and was very complex.
Use locks for sake of simplicity, following KISS principle.
Only remaining atomic operation use is time of day speed, because that
really is only read + written.

Also fixes a bug with m_time_conversion_skew only being decremented, never
incremented (Regresion from previous commit).

atomic.h changes:
	* Add GenericAtomic<T> class for non-integral types like floats.

	* Remove some last remainders from atomic.h of the volatile use.

It isn't possible to use atomic operations for floats, so don't use them there.

Having a lock is good out of other reasons too, because this way the float time
and the integer time both match, and can't get different values in a race,
e.g. when two setTimeofDay() get executed simultaneously.

Cleanup:
	* Remove volatile keyword, it is of no use at all. [1]
	* Remove the enable_if stuff. It had no use either.
	  The most likely explanation why the enable_if stuff was there is that it
	  was used as something like a STATIC_ASSERT to verify that sizeof(T) is not larger
	  than sizeof(void *). This check however is not just misplaced in a place where we
	  already use a lock, it isn't needed at all, as gcc will just generate a call to
	  to the runtime if it compiles for platforms that don't support atomic instructions.
	  The runtime will then most likely use locks.

Code style fixes:
	* Prefix name of the mutex
	* Line everything up nicely, where it makes things look nice
	* Filling \ continuations with spaces is code style rule

Added operations on the atomic var:
	* Compare and swap
	* Swap

The second point of the cleanup also fixes the Android build of the next commit.

[1]: http://stackoverflow.com/q/2484980

On Windows Release x64 bit build this changes:

ProfilerGraph::put
1.68% -> 0.061%

ProfilerGraph::draw
12% -> 17.%

So yes, there is a tradeoff between saving profiling data
(executed always) and drawing the profiler graph (executed very rarely).
But usually you don't have the profiler graph open.

Using logging for these just makes them bloated and hard to read and overally just not neat at all.

For several years now, the lua script lock has been completely broken.
This commit fixes the main issue (creation of a temporary rather than
scoped object), and fixes a subsequent deadlock issue caused by
nested script API calls by adding support for recursive mutexes.

When compiled with optimizations, the most recent versions of clang seem
to 'optimize' out a crucial "and %reg, 0x7FFFFFFF" instruction in noise2d(),
probably because it somehow assumed the variable n would never become greater
than that amount.
Indeed, signed integer underflow is undefined behavior in C and C++, so while
this optimization is "correct" in that sense, it breaks lots of existing code.
Solved by changing n to an unsigned type, making behavior well-defined.

Previously, the server called FATAL_ERROR when a Lua error occured.
This caused a (mostly useless) core dump.
The server now simply throws an exception, which is caught and printed before
exiting with a non-zero return value.
This also fixes a number of instances where errors were logged multiple times.

This allows the player to toggle continuous forward with a key (F by default),
so we don't have to hold down the forward key endlessly.

Increase default from 6 to 16 to help with mgv7 and mgfractal
Large-scale or alternative mapgens can result in a lowland spawn point not
being found, causing a spawn at (0, 0, 0) possibly buried underground
The max height is now settable to allow correct player spawn
in any mapgen or when using custom noise parameters

Use this macro to disallow copying of an object using the assignment
operator or copy constructor.  This catches otherwise silent-but-deadly
mistakes such as "ServerMap map = env->getMap();" at compile time.

If so desired, it is still possible to copy a class, but it now requires
an explicit call to memcpy or std::copy.

-> Put access to time variables under the time lock.
-> Merge both time locks, there is no point to have two locks.
-> Fix the lock being released too early in Environment::setTimeOfDay
-> Add serverside getter so that you don't have to get
	the environment if you only have the server

Also fix a potential seed truncation issue on platforms where the
range of ptrdiff_t (the underlying type of lua_Integer) is too small.

abort() doesn't benefit from the high level abstractions from FATAL_ERROR.

Remove outdated loglevel list from a l_util.cpp comment,
and rather point to the updated code.

Fixes #3280