bullet: Streamline bundling, remove extraneous src/ folder

Document version and how to extract sources in thirdparty/README.md.
Drop unnecessary CMake and Premake files.
Simplify SCsub, drop unused one.

thirdparty/bullet/BulletInverseDynamics/details/MultiBodyTreeInitCache.cpp

@@ -0,0 +1,113 @@
+#include "MultiBodyTreeInitCache.hpp"
+
+namespace btInverseDynamics {
+
+MultiBodyTree::InitCache::InitCache() {
+	m_inertias.resize(0);
+	m_joints.resize(0);
+	m_num_dofs = 0;
+	m_root_index=-1;
+}
+
+int MultiBodyTree::InitCache::addBody(const int body_index, const int parent_index,
+									  const JointType joint_type,
+									  const vec3& parent_r_parent_body_ref,
+									  const mat33& body_T_parent_ref,
+									  const vec3& body_axis_of_motion, const idScalar mass,
+									  const vec3& body_r_body_com, const mat33& body_I_body,
+									  const int user_int, void* user_ptr) {
+	switch (joint_type) {
+		case REVOLUTE:
+		case PRISMATIC:
+			m_num_dofs += 1;
+			break;
+		case FIXED:
+			// does not add a degree of freedom
+			// m_num_dofs+=0;
+			break;
+		case FLOATING:
+			m_num_dofs += 6;
+			break;
+		default:
+			error_message("unknown joint type %d\n", joint_type);
+			return -1;
+	}
+
+	if(-1 == parent_index) {
+		if(m_root_index>=0) {
+			error_message("trying to add body %d as root, but already added %d as root body\n",
+						  body_index, m_root_index);
+			return -1;
+		}
+		m_root_index=body_index;
+	}
+
+	JointData joint;
+	joint.m_child = body_index;
+	joint.m_parent = parent_index;
+	joint.m_type = joint_type;
+	joint.m_parent_pos_parent_child_ref = parent_r_parent_body_ref;
+	joint.m_child_T_parent_ref = body_T_parent_ref;
+	joint.m_child_axis_of_motion = body_axis_of_motion;
+
+	InertiaData body;
+	body.m_mass = mass;
+	body.m_body_pos_body_com = body_r_body_com;
+	body.m_body_I_body = body_I_body;
+
+	m_inertias.push_back(body);
+	m_joints.push_back(joint);
+	m_user_int.push_back(user_int);
+	m_user_ptr.push_back(user_ptr);
+	return 0;
+}
+int MultiBodyTree::InitCache::getInertiaData(const int index, InertiaData* inertia) const {
+	if (index < 0 || index > static_cast<int>(m_inertias.size())) {
+		error_message("index out of range\n");
+		return -1;
+	}
+
+	*inertia = m_inertias[index];
+	return 0;
+}
+
+int MultiBodyTree::InitCache::getUserInt(const int index, int* user_int) const {
+	if (index < 0 || index > static_cast<int>(m_user_int.size())) {
+		error_message("index out of range\n");
+		return -1;
+	}
+	*user_int = m_user_int[index];
+	return 0;
+}
+
+int MultiBodyTree::InitCache::getUserPtr(const int index, void** user_ptr) const {
+	if (index < 0 || index > static_cast<int>(m_user_ptr.size())) {
+		error_message("index out of range\n");
+		return -1;
+	}
+	*user_ptr = m_user_ptr[index];
+	return 0;
+}
+
+int MultiBodyTree::InitCache::getJointData(const int index, JointData* joint) const {
+	if (index < 0 || index > static_cast<int>(m_joints.size())) {
+		error_message("index out of range\n");
+		return -1;
+	}
+	*joint = m_joints[index];
+	return 0;
+}
+
+int MultiBodyTree::InitCache::buildIndexSets() {
+	// NOTE: This function assumes that proper indices were provided
+	//	   User2InternalIndex from utils can be used to facilitate this.
+
+	m_parent_index.resize(numBodies());
+	for (idArrayIdx j = 0; j < m_joints.size(); j++) {
+		const JointData& joint = m_joints[j];
+		m_parent_index[joint.m_child] = joint.m_parent;
+	}
+
+	return 0;
+}
+}