A fix and a test case for Bug#17843 "Certain stored procedures fail to

run at startup"

The server returned an error when trying to execute init-file with a 
stored procedure that could return multiple result sets to the client. 
A stored procedure can return multiple result sets if it contains 
PREPARE, SELECT, SHOW and similar statements.
   
The fix is to set client_capabilites|=CLIENT_MULTI_RESULTS in
sql_parse.cc:handle_bootstrap(). There is no "client" really, so 
nothing is ever sent. This makes init-file feature behave consistently: 
the prepared statements that can be called directly in the init-file 
can be used in a stored procedure too.

Re-committed the patch originally submitted by Per-Erik after review.

sql/sql_class.cc

@@ -1946,6 +1946,7 @@ void Security_context::init()
 {
   host= user= priv_user= ip= 0;
   host_or_ip= "connecting host";
+  priv_host[0]= '\0';
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   db_access= NO_ACCESS;
 #endif