Add the GC benchmark suite

gc/Makefile

gc/cacheprof/Arch_x86.hs

gc/cacheprof/Generics.hs

gc/cacheprof/Main.hs

gc/cacheprof/Makefile

gc/cacheprof/cacheprof.stdin

gc/cacheprof/cacheprof.stdout

gc/cacheprof/cacheprof_hooks2_x86.s

gc/circsim/Main.lhs

gc/circsim/Makefile

gc/circsim/circsim.faststdout

gc/circsim/circsim.stdout

gc/constraints/Main.hs

gc/constraints/Makefile

gc/constraints/constraints.faststdout

gc/constraints/constraints.stdout

gc/fibheaps/Main.lhs

gc/fibheaps/Makefile

gc/fibheaps/fibheaps.stdout

gc/fibheaps/orig