[BUILD] build fixes for Solaris

One build error in stream_sock.c when MSG_NOSIGNAL is not defined,
and a warning in task.c.
diff --git a/src/task.c b/src/task.c
index e91a26b..6f7b264 100644
--- a/src/task.c
+++ b/src/task.c
@@ -10,6 +10,8 @@
  *
  */
 
+#include <string.h>
+
 #include <common/config.h>
 #include <common/eb32tree.h>
 #include <common/memory.h>