Build: Fix javadoc errors with Oracle JDK

Tested with 12.0.2

core/java/src/gnu/getopt/package.html

@@ -11,6 +11,7 @@ Copyright (c) 1998 by Aaron M. Renn (arenn@urbanophile.com),
 LGPL v2.
 </p><p>
 Changes:
+</p>
 <ul><li>
 Simplified Chinese
 MessagesBundle_chs.properties renamed to MessagesBundle_zh.properties
@@ -21,5 +22,4 @@ MessagesBundle_cht.properties renamed to MessagesBundle_zh_TW.properties
 Norwegian Bokmaal
 MessagesBundle_no.properties renamed to MessagesBundle_nb.properties
 </li></ul>
-</p>
 </body></html>

core/java/src/net/i2p/app/package.html

@@ -7,12 +7,12 @@ the that interface instead of being started with main().
 </p>
 <p>
 The benefits for clients using this interface:
+</p>
 <ul>
 <li>Get the current context via the constructor
 <li>Complete life cycle management by the router
 <li>Avoid the need for static references
 <li>Ability to find other clients without using static references
 </ul>
-</p>
 </body>
 </html>

core/java/src/net/i2p/crypto/elgamal/package.html

@@ -4,7 +4,7 @@
    Copied from Bouncy Castle 1.53.
 </p><p>
    Since 0.9.25.
-</p><p><pre>
+</p><pre>
 
 
 Copyright (c) 2000 - 2013 The Legion of the Bouncy Castle Inc. (http://www.bouncycastle.org)
@@ -25,5 +25,5 @@ DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 
-</pre></p>
+</pre>
 </body></html>

core/java/src/org/json/simple/parser/Yylex.java

@@ -383,7 +383,7 @@ int getPosition(){
    *
    * All internal variables are reset, the old input stream 
    * <b>cannot</b> be reused (internal buffer is discarded and lost).
-   * Lexical state is set to <tt>ZZ_INITIAL</tt>.
+   * Lexical state is set to <code>ZZ_INITIAL</code>.
    *
    * @param reader   the new input stream 
    */
@@ -425,7 +425,7 @@ int getPosition(){
 
 
   /**
-   * Returns the character at position <tt>pos</tt> from the 
+   * Returns the character at position <code>pos</code> from the 
    * matched text. 
    * 
    * It is equivalent to yytext().charAt(pos), but faster