Bug#31752: check strmake() bounds

strmake() called with wrong parameters:
5.0-specific fixes.


client/mysql.cc:
  In debug-mode, strmake() fills unused part of buffer with
  a test-pattern. This overwrites our previous extra '\0'
  (from previous bzero()).
sql/sp.cc:
  off-by-one buffer-size.

client/mysql.cc

@@ -2987,7 +2987,10 @@ com_connect(String *buffer, char *line)
       Two null bytes are needed in the end of buff to allow
       get_arg to find end of string the second time it's called.
     */
-    strmake(buff, line, sizeof(buff)-2);
+    tmp= strmake(buff, line, sizeof(buff)-2);
+#ifdef EXTRA_DEBUG
+    tmp[1]= 0;
+#endif
     tmp= get_arg(buff, 0);
     if (tmp && *tmp)
     {

sql/sp.cc

@@ -1902,7 +1902,7 @@ sp_use_new_db(THD *thd, LEX_STRING new_db, LEX_STRING *old_db,
 
   if (thd->db)
   {
-    old_db->length= (strmake(old_db->str, thd->db, old_db->length) -
+    old_db->length= (strmake(old_db->str, thd->db, old_db->length - 1) -
                      old_db->str);
   }
   else