Circuit padding tests.

src/core/or/circuitpadding.c

src/core/or/circuitpadding.h

src/lib/smartlist_core/smartlist_foreach.h

src/lib/time/compat_time.c

src/lib/time/compat_time.h

src/test/Makefile.nmake

src/test/include.am

src/test/test.c

src/test/test.h

src/test/test_circuitpadding.c

src/test/test_containers.c