Fix fluid blocks

For https://github.com/BuildCraft/BuildCraft/issues/1843 .

src/main/java/net/minecraftforge/fluids/BlockFluidClassic.java

@@ -349,8 +349,6 @@ public class BlockFluidClassic extends BlockFluidBase
     @Override
     public boolean canDrain(World world, int x, int y, int z)
     {
-        return false; //isSourceBlock(world, x, y, z);
+        return isSourceBlock(world, x, y, z);
     }
-    @Override public Fluid getFluid(){ return null; }
-    @Override public float getFilledPercentage(World world, int x, int y, int z) { return 0; }
 }

src/main/java/net/minecraftforge/fluids/BlockFluidFinite.java

@@ -318,6 +318,4 @@ public class BlockFluidFinite extends BlockFluidBase
     {
         return false;
     }
-    @Override public Fluid getFluid() { return null; }
-    @Override public float getFilledPercentage(World world, int x, int y, int z) { return 0; }
 }