Shared system routines

[james.umcp-cs%udel-relay at sri-unix.UUCP]

From:  James O'Toole <james.umcp-cs at udel-relay>

On PRIME machines running the PRIMOS operating system, sharing
of library routines is accomplished via a strange call-by-name.
The name of the routine is provided to the OS, it looks up the address, and
MODIFIES the calling instruction to directly this address.  I
don't like this, but it works pretty well.