support count-based avalon fingerprint

[greglandrum]

Here's the relevant function from ssmatch.c

/*
* Counts the bit multiplicity in fp_counts[0..ncounts-1] that correspond to the paths
* with up to some defined size. which_bits is a set of flags that defines
* which algorithms are triggered. as_query must be set to TRUE if the
* fp_counts are to be computed for a query, which is mostly for hydrogen
* counts.
*
* exclude_atom is the number of the atom that must not be touched by each
* fragment. exclude_atom == 0 means all atoms.
*
* This function forwards to CountFingerprintPatterns().
*/
int SetFingerprintCountsWithFocus(struct reaccs_molecule_t *mp,
                                  int *fp_counts, int ncounts,
                                  int which_bits,
                                  int as_query,
                                  int fpflags,
                                  int exclude_atom)