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

server-tools/instance-manager/commands.h

@@ -163,6 +163,7 @@ public:
 class Syntax_error : public Command
 {
 public:
+  Syntax_error() {}
   int execute(struct st_net *net, ulong connection_id);
 };