small tweak to archive members in Makefile.in

librdstats.a(rd_stats.o count.o) in Makefile.in triggers a syntax error in gnumake.

make: *** No rule to make target `librdstats.a(rd_stats.o', needed by `librdstats.a'.  Stop.

Changing it to librdstats.a(rd_stats.o) librdstats.a(count.o)  seems to solve the problem.