clarify that $0 means this.

git-svn-id: http://anonsvn.jboss.org/repos/javassist/trunk@164 30ef5769-5b8d-40dd-aea6-55b5d6557bb3

tutorial/tutorial2.html

@@ -186,7 +186,7 @@ have special meaning:
 <ul><table border=0>
 <tr>
 <td><code>$0</code>, <code>$1</code>, <code>$2</code>, ... &nbsp &nbsp</td>
-<td>Actual parameters</td>
+<td><code>this</code> and actual parameters</td>
 </tr>
 
 <tr>
@@ -251,7 +251,7 @@ the class currently edited.</td>
 
 <p>The parameters passed to the target method
 are accessible with
-<code>$0</code>, <code>$1</code>, <code>$2</code>, ... instead of
+<code>$1</code>, <code>$2</code>, ... instead of
 the original parameter names.
 <code>$1</code> represents the
 first parameter, <code>$2</code> represents the second parameter, and
@@ -569,7 +569,7 @@ starting with <code>$</code> have special meaning
 <ul><table border=0>
 <tr>
 <td><code>$0</code>, <code>$1</code>, <code>$2</code>, ... &nbsp &nbsp</td>
-<td>Actual parameters</td>
+<td><code>this</code> and actual parameters</td>
 </tr>
 
 <tr>