pgsql: Fix Windows setitimer() emulation to not depend on delivering an

Log Message:
-----------
Fix Windows setitimer() emulation to not depend on delivering an APC
to the main thread. This allows removal of WaitForSingleObjectEx() calls
from the main thread, thereby allowing us to re-enable Qingqing Zhou's
CHECK_FOR_INTERRUPTS performance improvement. Qingqing, Magnus, et al.

Modified Files:
--------------
pgsql/src/backend/port/win32:
signal.c (r1.13 -> r1.14)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/signal.c.diff?r1=1.13&r2=1.14)
socket.c (r1.9 -> r1.10)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/socket.c.diff?r1=1.9&r2=1.10)
timer.c (r1.5 -> r1.6)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/timer.c.diff?r1=1.5&r2=1.6)
pgsql/src/include:
miscadmin.h (r1.182 -> r1.183)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/miscadmin.h.diff?r1=1.182&r2=1.183)
pgsql/src/include/port:
win32.h (r1.48 -> r1.49)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/port/win32.h.diff?r1=1.48&r2=1.49)