Direct all BlockPlaceEvents to a singular location. Fixes BUKKIT-3438

By having a single function to process BlockPlacement logic, we make
it so that there is consistent behavior throughout all BlockPlace
events. This should allow for easier troubleshooting and less diffs
in source.

This also fixes BUKKIT-3463 by including the correct coordinates that
were clicked to the event.

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

@@ -23,6 +23,7 @@ public class BlockMushroom extends BlockFlower {
     }
 
     public void b(World world, int i, int j, int k, Random random) {
+        final int sourceX = i, sourceY = j, sourceZ = k; // CraftBukkit
         if (random.nextInt(25) == 0) {
             byte b0 = 4;
             int l = 5;
@@ -48,12 +49,6 @@ public class BlockMushroom extends BlockFlower {
             j1 = j + random.nextInt(2) - random.nextInt(2);
             k1 = k + random.nextInt(3) - 1;
 
-            // CraftBukkit start - preserve source block coordinates
-            int sourceX = i;
-            int sourceY = j;
-            int sourceZ = k;
-            // CraftBukkit end
-
             for (int l1 = 0; l1 < 4; ++l1) {
                 if (world.isEmpty(i1, j1, k1) && this.d(world, i1, j1, k1)) {
                     i = i1;