I decided to not mess with actual casts. In retrospect, this is probably
for the best as it avoids any bit-cast conflicts, but should allow for
block initializers with a few tweaks. `@construct (type, args...)` in
Ruamoko follows the same path as `type(args...)` in glsl.
When the number of supplied vectors matches the number of columns in the
matrix and all vectors have the same width as the number of rows in the
matrix, there's no need to expand the vectors into components only to be
gathered again.
SPIR-V requires that matrices are constructed from vectors rather than
individual components. While not optimal, iqm.vert's output now passes
spirv-val. Also probably still lots wrong with fine details.
Arrays done via the field code since they use the same opcode and logic.
For now swizzles are just swizzles and don't support zeroing or negating
(but doing one or the other (not both) should be easy).
Now declarations can be deferred too, thus things like generic/template
and inline functions should be possible. However, the most important
thing is this is a step towards a cleaner middle layer for compilation,
separating front-end language from back-end code-gen.
