libstdc++ doesn't include <cstring> inside of <string>, unlike libc++.

Its a possible mistake to log in to a server with twice the same name.
Before, it triggered a server wide error message, now it logs to actionstream.

Work around irrlicht bug and hide nametag if its alpha is set to 0.
Thanks @TeTpaAka for pointing out workaround.

Specifically, the added rule matches .kate-swp files.

Commit 11a96e49
commented out version parsing, resulting in the version byte being parsed as part of the color,
making nametags dark grey.
Re-introduces version parsing and ignores the packet if the version is more recent than ours,
fixing the unused variable warning (should have been done anyway).

This improves performance of MapBlock::raiseModified by a factor of 6.
Also, clean up mapblock.h a bit and inline small functions.

This adds the ability to grab 'slices' of noise calculated by PerlinNoiseMap.
Retrieving smaller slices of noise from the computation result as needed
optimizes memory usage while maintaining a reasonable amount of CPU overhead.

Due to compatibility concerns, this is temporarily disabled.

  * The time command now accepts parameters in the form <hour>:<minute>,
    and if invoked with no parameters returns the current time in said format.

Also rename method to better match what it does.

This enables srp.

Before this commit autofast for Android was ignored if the user was sneaking, digging or building. There is no reason for this and it impedes movement control

Android terminated immediately after start since commit
181f7baa
because library wasn't loaded, and libminetest.so required
libgmp.so.10 instead of libgmp.so.

The second issue has been solved by the linker flags.

Items dropped into unloaded map space will crash game so here's a fix...

Don't ident too much, and add a comment.

Also optimize json's library

Adds everything needed for SRP (and everything works too),
but still deactivated, as protocol v25 init packets aren't final yet.
Can be activated by changing the LATEST_PROTOCOL_VERSION header to 25
inside networkprotocol.h.

Uses system provided libgmp if found, if not it falls back to mini-gmp.