Some compilers (notably MSVC) were using signed values for bitfield enums. This was causing problems where 2 bits were used to store 4 or less enum values, where they were being treated as negative numbers.
This PR explicitly requests these enums to be treated as unsigned values.
Allow AStar/AStar2D zero point weight.
Limit was set to 1 which seemed like an arbitrary value as lower values down to zero can be useful for common gameplay navigation elements like teleports.
