Fixes to common vulnerabilities found in IBM Db2 High Performance Unload

IBM DB2 High Performance Unload 6.1.0.3, 5.1.0.1, 6.1.0.2, 6.5, 6.5.0.0 IF1, 6.1.0.1, 6.1, and 5.1 could allow an authenticated user to cause the program to crash due to a buffer being overwritten when it is allocated on the stack.