Update to v2.1.19

It should says what on the tin.

See merge request !190

Ignore askinfoviams

Turns out PT_ASKINFOVIAMS is an obsolete packet type anyway, the MS doesn't send it at all. So let's just ignore it in the netcode then. (the online page just acts like a client and sends PT_ASKINFO, and is not part of the MS itself)

See merge request !191

Disable gettext

Disable Gettext support for Mingw32 builds

See merge request !154

Netcode hotfix

Various netcode fixes are included in this branch. Most important of all of course is a fix for the Net_CloseConnection invalid node -32769 detected message thing, or rather what actually caused that to occur.

It's a merge to master since everything here should be compatible with 2.1.18: the only main changes are related to recieving packets (whether you're the host of a netgame or a client), which AFAIK shouldn't cause desyncs if you played with these fixes on a 2.1.18-hosted netgame (or hosted a netgame with the fixes and 2.1.18-using players join you).

See merge request !185

A bunch of bugfixes about too many wads in netgames

Fixes:
* Having bunch of music WADs added and then breaching the file limit(s) through joining a server with important files added. http://mb.srb2.org/showthread.php?t=42662
* Having a bunch of music WADs added, joining a server, and then breaching the file limit(s) when the server adds a file. https://mb.srb2.org/showthread.php?t=34664
* Informing the adminplayer whenever they try to send a request addfile net command but the file limit(s) are reached.

Done into next because I might as well be 100% safe, even though this could probably work on master as well.

See merge request !187

Missiles 'n slopes

Fixed that thing where missiles like sliding up slopes for some reason.

This isn't a 1:1 fix compared to non-slopes - missiles still like stepping up over the borders of sloped sectors and will continue going as long as they never touch that ground again, whereas they can never step up on flat ones - but this fixes the most egregrious issue.

See merge request !181

Cleanup part 2, make ye old 2.1.18 warning a debugfile only message, and make the node == -1 have its own debugfile only message too

Also get rid of a stray newline

textcmd[0] for PT_NODETIMEOUT can't hold anything < 0 anyway, and you'd probably have to really try to get >= MAXNETNODES

Display node's IP when printing the "sending file to node n" message, if noticedownload is turned on

* if you sent it to a client rather than the server, game over, your connection is closed
* if files that don't exist or are too large are requested are listed, game over, your connection is closed (they should have been checked on YOUR side beforehand, silly)
* if the server has downloading disabled anyway, ...yeah, you get the idea

Don't worry, I made sure Got_RequestFilePak cleaned up the full file request list for the node in case of failure

NiGHTS capsule color fix

This fixes the Egg/Ideya capsule from NiGHTS stages being given SKINCOLOR_RED as a color. Not really relevant for vanilla SRB2 (since it doesn't use green in the sprite), but it may be relevant for custom mods using a custom NiGHTS capsule sprite that happens to use green.

See merge request !189

Exit your server desync fix

This branch fixes this bug: https://mb.srb2.org/showthread.php?t=41811

Here's an explanation of how this bug is actually happening:
* Pressing Enter with "Start" selected calls `D_MapChange` to make a map change command. (Note that part of it is actually delayed because it's called from a menu, but this isn't relevant to the bug)
* `D_MapChange` itself calls `SV_StartServer` to start up the server, if you're supposed to be the server player.
* Pressing Esc while starting up a server like shown in the gif causes the server to be cancelled, and go back to the title screen.
* HOWEVER, since we're still in `D_MapChange`, the map change command is made anyway.
* Since we're not in a netgame as expected, no random seed is added, and the map change command has a total size of 9 bytes (1 for the id + 8 for the actual data). This is then stored in the net command buffer. The random seed would add another 4 bytes if it WAS added, note.
* Next time you start a server, and let it work as normal, two more net commands are added: an "add player" command (size 3), and a map change command (size 13, including random seed this time). Your net command buffer now has a total size of **25** (9 + 3 + 13).
* This net command buffer is then sent as a `PT_TEXTCMD` packet to yourself.
* SRB2 recieves the `PT_TEXTCMD` you sent to yourself, and some time later, tries to run the net commands stored in it.
* The first map command is read as if it's size 13 rather than size 9 (it isn't), mistakeningly thinking a 4-byte random seed is stored (since you ARE in a netgame now). This means your buffer reads what it thinks is the next net command starting from position **[14]** in the buffer.
* Bad luck, it gets an id of **0**, which doesn't correspond with any net command!
* This message is then printed in the console:

> WARNING: Got unknown net command [14]=0 (max 25)

* The game subsequently kicks you out the server with a "desynch" message.

tl;dr The game doesn't correctly cancel the map change when you cancel the server with Esc like that. This is not a good thing.

See merge request !188

* Made the check in Got_RequestAddfilecmd more comprehensive, since I might as well. Just something to tweak a little later in internal.

Partial implementation of fix for Got_RequestAddfilecmd (the other half - the limitation on the size of the filesneeded section of the serverinfo packet - will be applied in internal.)

Added a bunch of missing checks to prevent non-server players from sending other non-server players stuff