Adding all Entities into CraftBukkit.

These are needed to properly allow for determining class type, in
accordance with current practice.

src/main/java/net/minecraft/server/EntitySpider.java

@@ -0,0 +1,79 @@
+package net.minecraft.server;
+
+import java.util.Random;
+
+public class EntitySpider extends EntityMobs {
+
+    public EntitySpider(World world) {
+        super(world);
+        aP = "/mob/spider.png";
+        a(1.4F, 0.9F);
+        bC = 0.8F;
+    }
+
+    public double k() {
+        return (double) J * 0.75D - 0.5D;
+    }
+
+    protected Entity l() {
+        float f1 = b(1.0F);
+
+        if (f1 < 0.5F) {
+            double d = 16D;
+
+            return ((Entity) (l.a(((Entity) (this)), d)));
+        } else {
+            return null;
+        }
+    }
+
+    protected String e() {
+        return "mob.spider";
+    }
+
+    protected String f() {
+        return "mob.spider";
+    }
+
+    protected String g() {
+        return "mob.spiderdeath";
+    }
+
+    protected void a(Entity entity, float f1) {
+        float f2 = b(1.0F);
+
+        if (f2 > 0.5F && W.nextInt(100) == 0) {
+            this.d = null;
+            return;
+        }
+        if (f1 > 2.0F && f1 < 6F && W.nextInt(10) == 0) {
+            if (A) {
+                double d = entity.p - p;
+                double d1 = entity.r - r;
+                float f3 = MathHelper.a(d * d + d1 * d1);
+
+                s = (d / (double) f3) * 0.5D * 0.80000001192092896D + s * 0.20000000298023224D;
+                u = (d1 / (double) f3) * 0.5D * 0.80000001192092896D + u * 0.20000000298023224D;
+                t = 0.40000000596046448D;
+            }
+        } else {
+            super.a(entity, f1);
+        }
+    }
+
+    public void a(NBTTagCompound nbttagcompound) {
+        super.a(nbttagcompound);
+    }
+
+    public void b(NBTTagCompound nbttagcompound) {
+        super.b(nbttagcompound);
+    }
+
+    protected int h() {
+        return Item.I.ba;
+    }
+
+    public boolean m() {
+        return B;
+    }
+}