A GDScript call to:
`multiplayer.network_peer.some_prop = true`
seems to transalte to:
```
var temp = multiplayer.network_peer
temp.some_prop = true
multiplayer.network_peer = temp
```
Which caused the MultiplayerAPI to be resetted.
The call to set_network_peer is now ignored if the peer that's beeing
set is the same as the currently set one.
rpc_sender_id is now correctly initialized to 0 so get_rpc_sender_id()
work reliably even if called before receiving any RPC.
root_node is initialized to NULL (fix crashes when incorrectly using the
MultiplayerAPI).
clear function now resets the packet cache size to free more memory when
not running.
This allows more consistency in the manner we include core headers,
where previously there would be a mix of absolute, relative and
include path-dependent includes.
This commit makes operator[] on Vector const and adds a write proxy to it. From
now on writes to Vectors need to happen through the .write proxy. So for
instance:
Vector<int> vec;
vec.push_back(10);
std::cout << vec[0] << std::endl;
vec.write[0] = 20;
Failing to use the .write proxy will cause a compilation error.
In addition COWable datatypes can now embed a CowData pointer to their data.
This means that String, CharString, and VMap no longer use or derive from
Vector.
_ALWAYS_INLINE_ and _FORCE_INLINE_ are now equivalent for debug and non-debug
builds. This is a lot faster for Vector in the editor and while running tests.
The reason why this difference used to exist is because force-inlined methods
used to give a bad debugging experience. After extensive testing with modern
compilers this is no longer the case.
