Write a new hack for getting sector->linecount from sector->lines in Lua, to put my mind at rest about it at last.

1) In sector_get, actually push the memory address of the lines array within sector_t, rather than push the value of "lines" itself (essentially, we we want a pointer to a double pointer, or rather a TRIPLE pointer haha)
2) In the sectorlines_* functions, use offsetof to shift the memory address so we can obtain the value of linecount within the sector_t struct, and dereference the result to obtain the value of linecount itself
3) ??? profit

Untested and uncompiled atm, but I have some confidence this might work