From my experience, two modifications need to be made to compile c35b2 with the REPDSTR keyword.
First, a module dependency is not set up correctly. It is necessary to edit build/UNX/dynamc.mk, scroll down to the lines beginning with:
It is necessary to add one more of these lines, with:
$(LIB)/dynamc.a(dcntrl.o) : $(LIB)/gener.a(repdstr.o)
Secondly, source/charmm/miscom.src must be edited, immediately after the lines:
use cross, only: CROSSINIT,QCROS
it is necessary to add:
For convenience, I have attached a diff of these changes. Once these were made, I was able to compile c35b2 with REPDSTR.