Limited sign text length to 15 characters, as per the spec.

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

@@ -0,0 +1,50 @@
+package net.minecraft.server;
+
+public class TileEntitySign extends TileEntity {
+
+    public String[] lines = new String[] { "", "", "", ""};
+    public int b = -1;
+    private boolean c = true;
+
+    public TileEntitySign() {}
+
+    public void b(NBTTagCompound nbttagcompound) {
+        super.b(nbttagcompound);
+        nbttagcompound.setString("Text1", this.lines[0]);
+        nbttagcompound.setString("Text2", this.lines[1]);
+        nbttagcompound.setString("Text3", this.lines[2]);
+        nbttagcompound.setString("Text4", this.lines[3]);
+    }
+
+    public void a(NBTTagCompound nbttagcompound) {
+        this.c = false;
+        super.a(nbttagcompound);
+
+        for (int i = 0; i < 4; ++i) {
+            this.lines[i] = nbttagcompound.getString("Text" + (i + 1));
+            if (this.lines[i].length() > 15) {
+                this.lines[i] = this.lines[i].substring(0, 15);
+            }
+        }
+    }
+
+    public Packet e() {
+        String[] astring = new String[4];
+
+        for (int i = 0; i < 4; ++i) {
+            astring[i] = this.lines[i];
+
+            // CraftBukkit start - limit sign text to 15 chars per line
+            if (this.lines[i].length() > 15) {
+                astring[i] = this.lines[i].substring(0, 15);
+            }
+            // CraftBukkit end
+        }
+
+        return new Packet130UpdateSign(this.e, this.f, this.g, astring);
+    }
+
+    public boolean a() {
+        return this.c;
+    }
+}