Don't overflow the result type of constant expressions.  Don't negate
unsigned types.  Define HAVE_STDBOOL_H for Visual C++ 2013 and later.

Thomas Munro
Reviewed-By: Michael Paquier and Tom Lane

Discussion: https://postgr.es/m/CAEepm%3D3%3DTDYEXUEcHpEx%2BTwc31wo7PA0oBAiNt6sWmq93MW02A%40mail.gmail.com