pregWeek cannot be set below 0 for new slaves

Several slave acquisition events are supposed to give you a slave who has just given birth, doing so by setting pregWeek to a negative value, but this doesn't work properly - pregWeek is reset to 0 automatically when you acquire the slave. This issue affects the following events:

• jeSlaveDisputeBreedingDeal
• reMalefactor ("anchorBaby")
• pAidResult ("seizedMission")
• desperateBirth
• FCTVshows (superfetation())

I've tested all of them except pAidResult and verified that all of them wind up with pregWeek === 0 once recruited, and have no reason to suspect that pAidResult would be any different.