Bug in evaluating (defined) expression with undef bits

This should set y=1, but verilator 6ce2a52 sets y=0 instead.

module issue_042(y);
  output [3:0] y;
  localparam [3:0] p11 = 1'bx;
  assign y = ~&p11;
endmodule

Self-contained test case: test013.v, test013.cc, test013.sh

History:
2014-05-11 Reported as Issue #764
2014-05-11 Fixed in GIT commit 5f5a3db