configure: Check for sys/time.h

Apparently this include is needed on some systems for building the
poll fallback (for the timeval struct for select?), but it isn't
available on all systems. Thus only include it if it exists.
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -1148,6 +1148,7 @@ HAVE_LIST="
     sys_resource_h
     sys_select_h
     sys_soundcard_h
+    sys_time_h
     sys_videoio_h
     threads
     trunc
@@ -2873,6 +2874,7 @@ check_header sys/mman.h
 check_header sys/param.h
 check_header sys/resource.h
 check_header sys/select.h
+check_header sys/time.h
 check_header unistd.h
 check_header vdpau/vdpau.h
 check_header vdpau/vdpau_x11.h

libavformat/os_support.c

@@ -58,7 +58,9 @@ int ff_win32_open(const char *filename_utf8, int oflag, int pmode)
 #if CONFIG_NETWORK
 #include <fcntl.h>
 #if !HAVE_POLL_H
+#if HAVE_SYS_TIME_H
 #include <sys/time.h>
+#endif
 #if HAVE_WINSOCK2_H
 #include <winsock2.h>
 #elif HAVE_SYS_SELECT_H