MEMORY add wrappers around all mallocs and frees and trace them

This patch adds a wrapper around all memory allocations and frees.
The idea is to get warned immediately if the application leaks memory.
Additionally the wrapper functions make it easy to add different
memory allocators or memory pools in the future.

include/iscsi.h

@@ -77,6 +77,7 @@ struct iscsi_url {
        char user[MAX_STRING_SIZE+1];
        char passwd[MAX_STRING_SIZE+1];
        int lun;
+       struct iscsi_context *iscsi;
 };
 
 /*