Circular bounding box selection shape

[elexis]

Selection shapes are square, but some buildings are round. Thus the player sometimes selects a building when trying to click on a unit standing behind it:

Everything in the green box is assumed to be the civic center when selecting.

input.js calling PickEntityAtPoint from Selection.cpp calls PickAllEntitiesAtPoint from CCmpUnitRenderer.cpp which uses a CBoundingBoxOriented to check for the things beneath the mouse cursor. In BoundingBoxOriented.h we find this unflagged TODO that would address this issue:

 * However, it could also be used to represent more generic shapes, such as parallelepipeds.

Most recently reported by !Djarskublar and briefly discussed in ​https://wildfiregames.com/forum/index.php?/topic/21502-building-clickmaps-not-aligned-well/