Fix a bunch of memory leak type bugs, and add some better

Fix a bunch of memory leak type bugs, and add some better
checking in places to make sure stuff is behaving properly.

base/statistics.cc:
    separate the per stat check from the general stats check.
    We always want the general stuff to happen
base/statistics.hh:
    -  separate the per stat check from the general stats check.
    we always want the general stuff to happen
    -  make every stat check that its bin is at least initialized
    -  set the vector2d x and y coordinates in init to prevent an
    uninitialized memory access
test/Makefile:
    don't need sim_time.o to test stats
test/stattest.cc:
    don't make x and y the same on the 2d test so that we make
    sure that the two dimensions are correct

--HG--
extra : convert_revision : 81320325056ac1c09f6842474fb6ee3bcc030a8e