Move NetFS to a package

This is based on Jalopeura's patch to #10191, however, there are some
changes.
From the patch:
* Make userlandfs use separate "interface definition" files for each
filesystem, so the netfs package can provide a configuration file
* Add a short document on how to use NetFS
* Various fixes to netfs to make it build again (volatile atomics)
* The netfs_mount script for easier use of NetFS

Additional fixes:
* Move netfs_mount and the interface description file to data/ in the
source tree
* Use strlcat instead of strcat to avoid a buffer overflow
* Some parts were already applied in previous commits

build/jam/packages/NetFS

@@ -0,0 +1,27 @@
+local netfsPackage = netfs.hpkg ;
+HaikuPackage $(netfsPackage) ;
+
+# userlandfs module
+AddFilesToPackage add-ons userlandfs : netfs ;
+
+# servers
+AddFilesToPackage servers : netfs_server ;
+AddFilesToPackage servers : authentication_server ;
+
+# tools
+AddFilesToPackage bin : netfs_config ;
+AddFilesToPackage bin : netfs_server_prefs ;
+AddFilesToPackage bin
+	: [ FDirName $(HAIKU_TOP) data bin netfs_mount ] ;
+
+# interface definition
+AddFilesToPackage data userlandfs file_systems
+	: [ FDirName $(HAIKU_TOP) data userlandfs file_systems netfs ]
+	: netfs ;
+
+# docs
+AddFilesToPackage documentation add-ons :
+	[ FDirName $(HAIKU_TOP) docs add-ons NetFS.html ] : NetFS.html ;
+
+BuildHaikuPackage $(netfsPackage) : netfs ;
+