Peter Allan analyzed the source code for the VAX780 simulator and
came up with a somewhat simple strategy to replicate the RP device
source code and to add another controller on an additional Massbus.
That initial strategy includes: Copying the pdp11_rp.c source module to
pdp11_rpb.c and making almost all global variables static as well as all
internal functions used in the RP device. All but the "DEVICE rp_dev",
that is, which now becomes "DEVICE rpb_dev" with a name of "RPB".
The change process was relatively simple although somewhat tedious and
wouldn't easily lend itself to manage future changes that might happen to
pdp11_rp.c.
The changes in this commit cleanup pdp11_rp.c so that changing it to
pdp11_rpb.c only need to affect 3 lines of code which will simplify
future maintenance of these modules.
bdb021e6ac