make: fix GCC warnings

*** 304,314 ****
                  report_dep(iflag, filename);
          }
  }
  
  void
! report_dependency(register char *name)
  {
          register char   *filename;
          char            buffer[MAXPATHLEN+1];
          register char   *p;
          register char   *p2;
--- 304,314 ----
                  report_dep(iflag, filename);
          }
  }
  
  void
! report_dependency(const char *name)
  {
          register char   *filename;
          char            buffer[MAXPATHLEN+1];
          register char   *p;
          register char   *p2;