FS Features

[Daggolin]

This pull request aims to improve a few FS related issues and to provide new features.

1. [MP] The fs_forceGame cvar from jk2mv. The user can set the force game on startup to ensure configs, screenshots, etc. are written to and read from the specified folder. The server provided fs_game value is still used for reading, so mods in custom folders and pk3s downloaded from the server should still work.

2. [MP] Files downloaded from the server get prefixed with dl_ in their name. Pk3s with this prefix are not loaded unless the server references them. If a server provides a pk3s that overrides all default textures, models, etc. it is only used on servers offering the same file for download. Playing on other servers the pk3 is ignored. This is ported form jk2mv as well.

3. [MP] Reflists from jk2mv. The reflists can be used to control file referencing when sv_allowDownload is enabled. For instance to only offer selected files (ref_whitelist.txt), block specific files (ref_blocklist.txt) and to offer files that wouldn't automatically be picked up by the download system (ref_forcelist.txt).

4. [Shared] Native libraries (dlls on Windows) are no longer automatically unpacked and used from pk3s, unless the game is started with com_unpackLibraries enabled.

5. [Shared] The network initialization is now performed before the filesystem initialization to avoid undesired side effects from network sockets having high fd values. For instance high kernel load on some systems due to high values in select calls.

6. [Shared] The fs_restart command from jk2mv. If no module has an active handle for a file within a pk3 the filesystem can be reloaded at runtime. This can be useful when testing/developing mods or when installing new maps, because intermediate map changes are no longer required to reload the filesystem.

7. [Shared] Increase pk3 limit. The hardcoded limit of 1024 files has been removed. The game tries to set the fd limit to 4096 on launch now. The start argument -maxfds can be used to override the default limit of 4096 (if the operating system permits the user to do so). This is ported from jk2mv as well.

The code ported from jk2mv was written by @ouned, @aufau, myself and possibly other contributors over time.