Merge branch 'mysql-5.6' into mysql-5.7

(cherry picked from commit 06db648de3b080bae518a083dd122ea10b058c04)

Author: Anushree Prakash B

client/mysql.cc

@@ -2581,7 +2581,10 @@ static bool add_line(String &buffer, char *line, size_t line_length,
       if (*in_string || inchar == 'N')	// \N is short for NULL
       {					// Don't allow commands in string
 	*out++='\\';
-	*out++= (char) inchar;
+        if ((inchar == '`') && (*in_string == inchar))
+          pos--;
+        else
+	  *out++= (char) inchar;
 	continue;
       }
       if ((com= find_command((char) inchar)))