* engine: change spec constants to simple list
For a shader program cache to be keyed on the set of spec constants that a
program has set, we need to know full exact list of constants, including their
default values. If we're going to always hold a list of all constants all the
time, then we may as well store them as a simple list where each index is the ID
number of the spec constant.
As part of this change, we now write the default values of spec constants into
the material file metadata.
* fix indent
* engine: fix sRGB swapchain emulation
075726db8b