[Ohrrpgce] SVN: teeemcee/10868 Shop stock levels are reset or adjusted when the shop thing is edited

[subversion at HamsterRepublic.com]

teeemcee
2018-11-18 23:20:04 -0800 (Sun, 18 Nov 2018)
500
Shop stock levels are reset or adjusted when the shop thing is edited

Changing thing type/id resets the stock instead of using garbage data.  If only
the stock level changed, the stock is increased/decreased by the change in the
initial stock level if possible.

This is accomplished by storing the type, id and initial stock of each shop
thing in gam.original_stock(), and in RSAV.

Also, I added a F6 debug key to shop thing editor to show stockidx.
And ohrhelp/test_game.txt was a bit out of date
---
U   wip/custom.bas
U   wip/game.bas
U   wip/game_udts.bi
U   wip/menustuf.rbas
U   wip/moresubs.rbas
U   wip/ohrhelp/shop_stuff.txt
U   wip/ohrhelp/test_game.txt
U   wip/savegame.rbas
U   wip/whatsnew.txt