MeshViewer : Camera update and small object tweak.
             ortho to perspective transition is now perfect.

to get M_PI from the platform headers and cast it to float.

static method that we can do without.

computation function.

compilation time for very little benefit and maybe even confusion.

- removed 0 CR characters
 - removed 188 trailing whitespaces
 - replaced 537 tabs with spaces

TODO : second pass on coding-style, and some tweak & usage modification.

computed on demand with static initialisation.

fully initialised.

functions; also remove a lot of idiotic "using namespace std" from the
codebase.

to the Tait-Bryan angles we had for now). Also, change quaternion storage
order to wxyz in order to match the constructors.

more unit tests for the quaternion to 3×3 matrix conversion.

with the unit tests.

Euler angles to a rotation matrix. Also fix quat::rotate() which was not
building the correct quaternion.

mathematical writing, and add static constructors to create quaternions
from a rotation.

code for all matrices.

replace the well known DeBruijn sequence with a custom magic value to spare
one binary operation.

"shader" source directory since we have "gpu".