Ammo quantity upgrade prototype

Not yet tested. Will crash until I also get rate_upgrade_opt up.

vacuum_gambit.p8

@@ -676,7 +676,8 @@ bullet_base = mknew{ }
 
 gun_base = mknew{ 
  shoot_ready = -32768,
- icon = 20
+ icon = 20,
+ ammobonus = 1,
 }
 
 -- gun_base subtypes are
@@ -707,6 +708,38 @@ function gun_base:actually_shoot(x, y)
  self.munition.new{}:spawn_at(x, y)
 end
 
+-- upgrade 
+function gun_base:small_upgrade_opts()
+ local ret = {
+  self:ammo_upgrade_opt(),
+  self:rate_upgrade_opt(),
+ }
+ local s = self.special_upgrade_opt
+ if (s) add(ret, s(self))
+ return ret
+end
+
+function gun_base:ammo_upgrade_opt()
+ local a=self.maxammo
+ local x=a\10+self.ammobonus
+ return {
+  icon=self.icon,
+  hdr=self.hdr,
+  body=[[----------AMMO
+
+ more shots.
+
+   is: ]]..tostr(a)..[[
+  add: ]]..tostr(x)..[[
+----------
+total: ]]..tostr(a+x),
+  action=function()
+   self.maxammo+=x
+   self.ammo+=x
+  end,
+ }
+end
+
 function bullet_base:hitship(_)
  self:die()
  return true