d_camera improvements (part 1) (#2623)

* Rename several dCamera_c fields

* Refactor mWork to generic buffer instead of union

* d_camera match improvements

* Implement several dCamera_c functions

* Remove d_camera.h from PCH

The symbol names in d_camera indicate that this header wasn't
included in the PCH (as they're compiled directly in d_camera.cpp).

src/d/actor/d_a_obj_smallkey.cpp

@@ -10,6 +10,7 @@
 #include "d/actor/d_a_player.h"
 #include "d/d_item_data.h"
 #include "d/d_tresure.h"
+#include "f_op/f_op_camera_mng.h"
 
 /* 80CDB7F4-80CDB838 000000 0044+00 6/6 0/0 0/0 .rodata          l_cyl_src */
 const static dCcD_SrcCyl l_cyl_src = {