java: fix parser stack popping bug.

Reported at
<http://lists.gnu.org/archive/html/bug-bison/2011-02/msg00005.html>.
* THANKS (Angelo Borsotti): Add.
* data/lalr1.java (YYParser::YYStack::pop): Fix off-by-one error
in clearing the value stack.  Previously, the top element of the
stack wasn't cleared and so the value was not garbage collected.
(cherry picked from commit 6f75992be5)

Conflicts:

	data/lalr1.java

THANKS

@@ -8,6 +8,7 @@ Alexander Belopolsky      [email protected]
 Alexandre Duret-Lutz      [email protected]
 Andreas Schwab            [email protected]
 Andrew Suffield           [email protected]
+Angelo Borsotti           [email protected]
 Anthony Heading           [email protected]
 Arnold Robbins            [email protected]
 Art Haas                  [email protected]