Refactor|Map Renderer|Client: Angle clipper now uses de::VectorN<>
API: Use Mobj_Sector() to determine the sector at the mobj's origin

Rather than using the DMU_API to resolve the sector from a BSP leaf
directly, plugins should now use Mobj_Sector() to determine this.

The map API is now at version #3 (DE_API_MAP = 1102).
API: DD_BASE_DDMOBJ_ELEMENTS() now records the BSP leaf at the origin
API: Replaced P_BspLeafAtPoint_FixedPrecision()

Plugins should now use P_SectorAtPoint_FixedPrecision() to determine
the sector at some arbitrary point in the current map. Previously it
was necessary to first determine the BSP leaf at that point and then
use the DMU API to obtain the attributed sector. Behavior/outcome is
not affected.
API: BSP leafs and nodes have no public properties

The map's BSP components no longer have any properties which can be
addressed via the DMU API. Also, it is no longer possible to use a
BSP leaf pointer to implicitly refer to a property of the attributed
sector.
libcommon: Cleanup polyobj lookup
libcommon: Cleanup
Merge branch 'master' of github.com:skyjake/Doomsday-Engine
Merge branch 'master' of github.com:skyjake/Doomsday-Engine
API: Standardized argument order of map API callback/traverser functions

P_Callback, P_Callbackp and P_Iteratep now use the same conventions
as the rest of the map API functions (i.e., callback then context).
Fixed|Map Renderer|BlockmapVisual|Client: Missing polyobj lines on blockmap debug visualizer
API: Combined map line box iterator functions

There is now only one function for iterating the map lines within a
user-defined AABox in map space, named P_LinesBoxIterator. Flags are
used specify which type(s) of map line are to be processed. Behavior
is unchanged.
Cleanup|World|Map: Minor internal map API cleanup
libcommon: Consolidated mobj state change functions; cleanup