Defines starting with `r' in machdep/ppc

• RBITS machdep/ppc/unix_signal.c:53
• rc machdep/ppc/bcopy.s:107
• rcr0 machdep/ppc/nkdefs.h:46
• rcr1 machdep/ppc/nkdefs.h:47
• rcr2 machdep/ppc/nkdefs.h:48
• rcr3 machdep/ppc/nkdefs.h:49
• rcr4 machdep/ppc/nkdefs.h:50
• rcr5 machdep/ppc/nkdefs.h:51
• rcr6 machdep/ppc/nkdefs.h:52
• rcr7 machdep/ppc/nkdefs.h:53
• rd machdep/ppc/bcopy.s:106
• RegIndex machdep/ppc/nkdefs.h:132
• RELOC machdep/ppc/lowmem_vectors.s:67
• rpa machdep/ppc/asm.h:50
• rs machdep/ppc/bcopy.s:105