It took two days of searching, but I finally found the page where it explains the few CL enhancements offered in the Technology Refreshes (TR1 through TR5).
The good news is that they offer weird *PRV support. That is you can use them in CL programs on V7R1 systems only, however you may also specify any valid target release (TGTRLS) value (back to V5R4) when creating the programs. However the new built in functions are only available on V7R1 systems. That is, the runtime is supported back to v5r4, but the source compiler won't work with them on a V5R4 machine. So you have to be on V7R1 to compile. (Requires PTF SE54031)
Interestingly, this is the exact architecture I recommended IBM move to for all its compilers.
Previously introduced CL built-in functions include: