sphere generation cleanups

git-svn-id: svn://svn.code.sf.net/p/sauerbraten/code/src@5040 07af1644-1164-4067-b897-63bf4dc9b748
fix crash when texture list is empty

git-svn-id: svn://svn.code.sf.net/p/sauerbraten/code/src@5041 07af1644-1164-4067-b897-63bf4dc9b748
make server_entity::spawned a bool

git-svn-id: svn://svn.code.sf.net/p/sauerbraten/code/src@5042 07af1644-1164-4067-b897-63bf4dc9b748
New version.