Allow unsigned types in PHY_ScalarType enum

[germangb]

Bullet should allow more unsigned types in the PHY_ScalarType enum. Right now It is not possible to use unsigned data in a ´btHeightfieldTerrainShape´ without manually converting it to signed. I understand this might affect bullet in sevaral other places. Is there a plan to add more types in the future?

bullet3/src/BulletCollision/CollisionShapes/btConcaveShape.h

Lines 23 to 32 in 79d24db

	/// PHY_ScalarType enumerates possible scalar types.
	/// See the btStridingMeshInterface or btHeightfieldTerrainShape for its use
	typedef enum PHY_ScalarType {
	PHY_FLOAT,
	PHY_DOUBLE,
	PHY_INTEGER,
	PHY_SHORT,
	PHY_FIXEDPOINT88,
	PHY_UCHAR
	} PHY_ScalarType;