Fixed compiler warnings detected by option -Wshadow and -Wunused:

- Removed not used variables and functions
- Added #ifdef around code that is not used
- Renamed variables and functions to avoid conflicts
- Removed some not used arguments

Fixed some class/struct warnings in ndb
Added define IS_LONGDATA() to simplify code in libmysql.c

I did run gcov on the changes and added 'purecov' comments on almost all lines that was not just variable name changes

mysql-test/r/mysqlcheck.result

@@ -1,3 +1,6 @@
+DROP TABLE IF EXISTS t1;
+drop view if exists v1;
+drop database if exists client_test_db;
 mysql.columns_priv                                 OK
 mysql.db                                           OK
 mysql.func                                         OK