Attached are a set of patches that allow reading of NRPN midi data.
I ended up modifying the MCHNBLK data structure in csoundCore.h to add nrpn related status bookkeeping (trying to follow the style of the existing storage of control data), and similarly copying the operation of the ctrl7 opcode and its usage of the control data array to make a new "nrpnin" opcode.
If you would like I can try to copy the existing ctrl7 manual page and edit it as appropriate to document nrpnin, but realistically in the near future I will be more interested in using the new nrpn data I can now use to control my synths than I will be in editing a help file :)
If someone would like to review / test my code and / or work on the documentation I would be very appreciative, I will be testing the code for the next few days myself (using it to make some music that is).
The naming of the diff files is a bit weird, but I hope you can puzzle out the meaning -- let me know if you want the diffs in a particular format or if you prefer I just send you the whole file so you can generate the diffs yourselves or whathaveyou.
I will gladly hand over copyright to the owners of csound, but would appreciate a little note indicating my contribution if this code ends up being used in csound.