removed gratuitous code about dynamic memory related to pspan detection.
break finger-matching into a separate helper function
replace struct atp_stroke with atp_stroke_t
rename wsp_finger_to_match as wsp_finger_t
simplify function declarations by dropping parameter names.
rename atp_config as atp_xfer_config
oops: atp_small_movement_threshold should have consistent value in SYSCTL