core.check_player_privs accepts as first argument a name or player object, but just tested for a string.
This caused crashes inside builtin, when being passed any unexpected types.

This provides a better (duck-typing like) test, better error reporting.

Add documentation, move files to a proper place and avoid memory leaks.
Make it work with most kind of texts, and allow backgrounds too.

Colored chat working as expected for both freetype and non-freetype builds. @nerzhul improvements * Add unit tests * Fix coding style * move guiChatConsole.hpp to client/

This fixes the problem that the first timer tick is an
overrun and causes all timers to expire immediately.

replaces #4003

This allows mods to perform both asynchronous and synchronous HTTP
requests. Mods are only granted access to HTTP APIs if either mod
security is disabled or if they are whitelisted in any of the
the secure.http_mods and secure.trusted_mods settings.

Adds httpfetch_caller_alloc_secure to generate random, non-predictable
caller IDs so that lua mods cannot spy on each others HTTP queries.

I could honestly not make much sense of the timer implementation
that was here. Instead I've implemented the type of timer algorithm
that I've used before, and tested it instead.

The concept is extremely simple: all timers are put in an ordered
list. We check every server tick if any of the timers have
elapsed, and execute the function associated with this timer.

We know that many timers by themselves cause new timers to be
added to this list, so we iterate *backwards* over the timer
list. This means that new timers being added while timers are
being executed, can never be executed in the same function pass,
as they are always appended to the table *after* the end of
the table, which we will never reach in the current pass over
all the table elements.

We switch time keeping to minetest.get_us_time(). dtime is
likely unreliable and we have our own high-res timer that we
can fix if it is indeed broken. This removes the need to do
any sort of time keeping.

The callback can now be invoked with either the player object or name as
the first parameter, and with either a table or a list of strings, like
this:

    minetest.check_player_privs(player_name, { shout = true, fly = true })
    minetest.check_player_privs(player_name, "shout", "fly")
    minetest.check_player_privs(player, { shout = true, fly = true })
    minetest.check_player_privs(player, "shout", "fly")

* abort if theres no active timer
* only reduce the timer.time of all timers when its necessary
* move updating timers_to_add into a seperate function

Add optional core.pos_to_string decimal place rounding
Move core.string_to_pos to builtin/common/misc_helpers.lua for consistency

Instead of collecting all objects within a huge radius (which could be
a big value), just register each player that connects and give back the
current hold list.

On the lua side, notably minetest.env:<function>(<args>) should now
be replaced by minetest.<function>(<args>).
The old way is and will stay supported for a long time.

Also:
Update and clean up lua_api.txt (by celeron55)
Move EnvRef to lua and remove add_rat and add_firefly (by kahrl)
Add separate src/util/CMakeLists.txt, other minor fixes (by kahrl)

Add ObjRef:is_player() and modify ObjRef:get_player_name() to always return a string to aid better inter-object compatibility of code that assumes objects to be players