allow map_cursor to be made from abs pos

[PatrikLundell]

Summary

None

Purpose of change

Allow map_cursor to be created from an absolute position in addition to a bubble one.
Given that it's stored as an absolute position internally (except for the weirdo case which may or may not exist), it makes sense to allow it to be stored directly.
Also silenced a couple of trivial compiler warnings as a by-catch.

Describe the solution

Add another creation operation and convert the usages where an absolute position was converted into a bubble one to use the new operation instead.

Describe alternatives you've considered

• Add operation to extract the absolute position, but there don't seem to be much use for it.
• Address the compiler warning about game.cpp operation rate_action_eat, line 1901 which is clearly incorrect, as a check whether a value differs from either if two constants is always going to be true. The compiler suggests || should be &&, which seems reasonable. However, I don't know that's what's intended.
• Get rid of the weirdo logic to handle usage of map_cursor prior to the existence of a valid "g" pointer. However, while I haven't seen anything clearly requiring it, I cannot rule out that there actually are cases where this is needed.

Testing

Load a save with a driving car and drive until it hit stuff. There should be no functional changes.

Additional context