Keeping some required nonstandard z/OS macros in their original libraries

The assembly of certain IMS modules requires z/OS® macros not contained on the standard z/OS System Macro libraries. Because these requirements are subject to change due to IMS and z/OS maintenance, keep these macros in their original libraries, and use the JCL generated by IMS for SYS1.MODGEN (or SYS1.AMODGEN).