(svn r2131) -Fix: Rewrite CmdBuildSingleRail(), this addresses several issues:
- Check input parameters for validity
- Adhere patch settings - you were able to build foundations under bridges even if foundations where deactivated
- Charge for foundations in all cases - foundations under bridges were for free
- Make the control flow more clear

static const SpriteID _draw_tunnel_table_1[] = {
	0x93D, 0x955,
};