This means the shared memory struct is just 255 bytes longer than a few
commits ago instead of 32K.
Also introduce a function for putting path strings in the shared memory
as there was too much copied and pasted code and it was error-prone.
Also free some handles once we're done with them so they don't leak.
Manual port of https://gitlab.com/OpenMW/openmw/-/merge_requests/3221 to OpenMW 0.48
