Remove redundant includes from dtls1.h

There were a set of includes in dtls1.h which are now redundant due to the
libssl opaque work. This commit removes those includes, which also has the
effect of resolving one issue preventing building on windows (i.e. the
include of winsock.h)

Reviewed-by: Andy Polyakov <appro@openssl.org>
diff --git a/ssl/d1_lib.c b/ssl/d1_lib.c
index a1d2032..6946b32 100644
--- a/ssl/d1_lib.c
+++ b/ssl/d1_lib.c
@@ -64,6 +64,12 @@
 
 #if defined(OPENSSL_SYS_VMS)
 # include <sys/timeb.h>
+#elif defined(OPENSSL_SYS_NETWARE) && !defined(_WINSOCK2API_)
+# include <sys/timeval.h>
+#elif defined(OPENSSL_SYS_VXWORKS)
+# include <sys/times.h>
+#elif !defined(OPENSSL_SYS_WIN32)
+# include <sys/time.h>
 #endif
 
 static void get_current_time(struct timeval *t);