Fix insnToString not accepting AbstractInsnNode (#53)

Author: Jonathing

src/main/java/net/minecraftforge/coremod/api/ASMAPI.java

@@ -556,15 +556,15 @@ public static String methodNodeToString(MethodNode node) {
      * @param insn The instruction to convert.
      * @return The string representation of the instruction.
      */
-    public static String insnToString(InsnNode insn) {
+    public static String insnToString(AbstractInsnNode insn) {
         Textifier text = new Textifier();
         insn.accept(new TraceMethodVisitor(text));
         return toString(text);
     }
 
     /**
      * Converts a {@link InsnList} to a string representation, displaying each instruction in the list similar to
-     * {@link #insnToString(InsnNode)}.
+     * {@link #insnToString(AbstractInsnNode)}.
      *
      * @param list The list to convert.
      * @return     The string