[Click] AverageCounter and 64bits

[rchertov]

So at some point Eddie introduced counter_t type, which is either 32bit 
or 64 bit depending on the machine architecture.  However, 
AverageCounter still uses atomic_uint32_t.  On a 10GE network, byte_rate 
wraps around quite rapidly, so a 64bit value would be useful.  I suppose 
one approach would be create atomic_counter_t which is either 32 or 64 
bit, or the alternate approach would be to use counter_t along with a 
lock.  Eddie which version would you prefer?

Roman