* Return usable count in zone of playerid's MZONE or SZONE(0~4) when uplayer moves pcard to playerid's field (can be negative).
* for LOCATION_MZONE, "usable" means not used, not disabled, satisfying EFFECT_MUST_USE_MZONE, satisfying EFFECT_MAX_MZONE
* for LOCATION_SZONE, "usable" means not used, not disabled, satisfying EFFECT_MAX_SZONE
*
* @param pcard the card about to move
* @param playerid the target player
* @param location LOCATION_MZONE or LOCATION_SZONE
* @param uplayer the request player, PLAYER_NONE means ignoring EFFECT_MUST_USE_MZONE of uplayer, ignoring EFFECT_MAX_MZONE, EFFECT_MAX_SZONE of playerid
* @param reason location reason
* @param zone specified zones, 0xff by default
* @param list storing unavailable or unspecified zones
*
* @return usable count in zone of playerid's MZONE or SZONE(0~4) (can be negative)