pgsql: Rearrange include file contents into a saner order, add inclusion

Log Message:
-----------
Rearrange include file contents into a saner order, add inclusion of
<signal.h>. Per Andrew Dunstan.

Modified Files:
--------------
pgsql/src/include/port:
win32.h (r1.41 -> r1.42)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/port/win32.h.diff?r1=1.41&amp;r2=1.42)