Handle combined instrument states of ENABLED and/or TIMED:

ENABLED TIMED
1 1 Aggregate stats, increment counter
1 0 Increment counter
0 1 Do nothing
0 0 Do nothing 

storage/perfschema/pfs.cc:
  Aggregate stats only if state is both ENABLED and TIMED. If ENABLED
  but not TIMED, only increment the value counter.
storage/perfschema/pfs_stat.h:
  Split aggregate and counter increment into separate
  methods for performance.