[configure] Refine CLOCK_MONOTONIC test

* configure.ac: Check for the actual CLOCK_MONOTONIC symbol, as clock_gettime
  need not imply that clock type is supported
* lib/zebra.h: use the method given in autoconf docs for sys/time.h
  inclusion
diff --git a/configure.ac b/configure.ac
index c1f6182..3ac8384 100755
--- a/configure.ac
+++ b/configure.ac
@@ -391,7 +391,7 @@
 AC_CHECK_HEADERS([stropts.h sys/ksym.h sys/times.h sys/select.h \
 	sys/types.h linux/version.h netdb.h asm/types.h \
 	sys/param.h limits.h signal.h libutil.h \
-	sys/socket.h netinet/in.h])
+	sys/socket.h netinet/in.h time.h sys/time.h])
 
 dnl Utility macro to avoid retyping includes all the time
 m4_define([QUAGGA_INCLUDES],
@@ -425,6 +425,16 @@
 #if HAVE_NETINET_IN_H
 # include <netinet/in.h>
 #endif
+#ifdef TIME_WITH_SYS_TIME
+# include <sys/time.h>
+# include <time.h>
+#else
+# ifdef HAVE_SYS_TIME_H
+#  include <sys/time.h>
+# else
+#  include <time.h>
+# endif
+#endif /* TIME_WITH_SYS_TIME */
 ])dnl
 
 AC_CHECK_HEADERS([sys/un.h net/if.h netinet/in_systm.h netinet/in_var.h \
@@ -1324,12 +1334,10 @@
 dnl --------------------------------------
 dnl checking for clock_time monotonic struct and call
 dnl --------------------------------------
-AC_CHECK_LIB(rt, clock_gettime,
-[AC_DEFINE(HAVE_MONOTONIC_CLOCK,, Have monotonic clock)
- LIBS="$LIBS -lrt"]
-)
-
-
+AC_CHECK_DECL(CLOCK_MONOTONIC,
+	[AC_CHECK_LIB(rt, clock_gettime, [LIBS="$LIBS -lrt"])
+	 AC_DEFINE(HAVE_MONOTONIC_CLOCK,, Have monotonic clock)
+], [AC_MSG_RESULT(no)], [QUAGGA_INCLUDES])
 
 dnl -------------------
 dnl capabilities checks
diff --git a/lib/zebra.h b/lib/zebra.h
index 2716460..2dc8451 100644
--- a/lib/zebra.h
+++ b/lib/zebra.h
@@ -55,7 +55,6 @@
 #include <sys/select.h>
 #endif /* HAVE_SYS_SELECT_H */
 #include <sys/stat.h>
-#include <sys/time.h>
 #include <sys/types.h>
 #include <sys/param.h>
 #ifdef HAVE_SYS_SYSCTL_H
@@ -72,7 +71,16 @@
 #include <sys/ksym.h>
 #endif /* HAVE_SYS_KSYM_H */
 #include <syslog.h>
-#include <time.h>
+#ifdef TIME_WITH_SYS_TIME
+# include <sys/time.h>
+# include <time.h>
+#else
+# ifdef HAVE_SYS_TIME_H
+#  include <sys/time.h>
+# else
+#  include <time.h>
+# endif
+#endif /* TIME_WITH_SYS_TIME */
 #include <sys/uio.h>
 #include <sys/utsname.h>
 #ifdef HAVE_RUSAGE