Matrix4x4 was defined as a derived class of Matrix<N,T> before.
Furthermore, some code was duplicated and it was overall just messy.
This commit turns Matrix4x4 into a simple alias for Matrix<4,T>.
Matrix elements were interpreted in different ways.
This makes it definitely row-major, allowing initialization via
initializer list in a standard scientific order. Also matrix
multiplication now happens in the correct order and accessing
elements happens as m_elements[row][column].
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
