Debug drawing

The library never draws. It fills an mnavDebugBuffer the host owns with vertices and two index lists, triangles and lines, which any renderer can draw. Its capacities and counts are of vertices, triangles and lines, as in mnavTriangleMesh: the triangle list holds three indices for each triangle and the line list two for each line, so a renderer draws 3 * triangleCount and 2 * lineCount indices.

Vertices are three floats relative to the buffer's origin, a world position in doubles, so the precision is kept where the camera is. Set the origin near what is being looked at.
Kinds, not colors. Each vertex carries what it shows (mnavDebugKind) and a value: the area type of a polygon's fill, whether tile links join a tile side, a link's kind with 256 added when it is detached or disabled, a polygon's place in a corridor, an open flight block's side. The host picks the colors.
Appending. Every debug call appends, so one buffer can hold a frame's worth of drawing. A full buffer returns mnav_errorCapacity with the counts the whole would need; grow it to those counts and draw again.

Function	Draws
`mnavNavmesh_Debug`	Polygons by area, inner edges, walls, tile sides and tile bounds, over an `mnavTileRange` of tile places, or every tile for NULL.
`mnavNavmesh_DebugLinks`	Every off-mesh link as an arc, at its snapped ends when attached.
`mnavDebugPath`, `mnavNavmesh_DebugCorridor`	A path's straight line; a corridor's polygons.
`mnavGridFlow_Debug`, `mnavNavFlow_Debug`	An arrow for each cell or polygon with a way on.
`mnavAvoidance_Debug`	Each agent's outline and a line to each neighbor `mnavAvoidance_Avoid` would give it.
`mnavAvoidance_Debug3D`	Each flier as three rings, its neighbors, and the spheres it avoids.
`mnavFlightVolume_Debug`	A flight volume's open blocks inside a box, as wire boxes. Solid space shows as gaps.
`mnavDebugFlightPath`	A flight path's steps.

The avoidance drawings check their input as mnavAvoidance_Avoid and mnavAvoidance_Avoid3D do, so drawing what a step would refuse is refused too. A bake's own debug output is its report.