Don't include sys/poll.h anymore.

poll.h is mandated by Single Unix Spec v2, the usual baseline for
postgres on unix.  None of the unixoid buildfarms animals has
sys/poll.h but not poll.h.  Therefore there's not much point to test
for sys/poll.h's existence and include it optionally.

Author: Andres Freund, per suggestion from Tom Lane
Discussion: https://postgr.es/m/20505.1492723662@sss.pgh.pa.us

configure

@@ -10600,7 +10600,7 @@ fi
 ## Header files
 ##
 
-for ac_header in atomic.h crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/poll.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h
+for ac_header in atomic.h crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"

configure.in

@@ -1179,7 +1179,7 @@ AC_SUBST(UUID_LIBS)
 ## Header files
 ##
 
-AC_CHECK_HEADERS([atomic.h crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/poll.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h])
+AC_CHECK_HEADERS([atomic.h crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h])
 
 # On BSD, test for net/if.h will fail unless sys/socket.h
 # is included first.

src/backend/storage/ipc/latch.c

@@ -42,9 +42,6 @@
 #ifdef HAVE_POLL_H
 #include <poll.h>
 #endif
-#ifdef HAVE_SYS_POLL_H
-#include <sys/poll.h>
-#endif
 
 #include "miscadmin.h"
 #include "pgstat.h"

src/include/pg_config.h.in

@@ -557,9 +557,6 @@
 /* Define to 1 if you have the <sys/ipc.h> header file. */
 #undef HAVE_SYS_IPC_H
 
-/* Define to 1 if you have the <sys/poll.h> header file. */
-#undef HAVE_SYS_POLL_H
-
 /* Define to 1 if you have the <sys/pstat.h> header file. */
 #undef HAVE_SYS_PSTAT_H
 

src/include/pg_config.h.win32

@@ -417,9 +417,6 @@
 /* Define to 1 if you have the <sys/ipc.h> header file. */
 /* #undef HAVE_SYS_IPC_H */
 
-/* Define to 1 if you have the <sys/poll.h> header file. */
-/* #undef HAVE_SYS_POLL_H */
-
 /* Define to 1 if you have the <sys/pstat.h> header file. */
 /* #undef HAVE_SYS_PSTAT_H */
 

src/interfaces/libpq/fe-misc.c

@@ -46,9 +46,6 @@
 #ifdef HAVE_POLL_H
 #include <poll.h>
 #endif
-#ifdef HAVE_SYS_POLL_H
-#include <sys/poll.h>
-#endif
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
 #endif