I forgot to set the alpha blend mode in the NanoVG changes which meant
that the code used additive blending by default which is not good if the
color in use is black. This sets the blend mode to the value that
corresponds to the values used by the NanoVG reference code.
There is nothing specific to OpenGL in that code anymore since it's all
handled in the shaders at this point. This will make the lighting
information available in the normal graphics code which allows to use
those values when filling the uniform buffer for the model rendering.
All transformations are now handled by shaders so there is nothing
special going on in the graphics API specific code anymore. Since model
uniform buffers require access to these matrices I moved the matrix
handling out of the graphics API code.
This introduces a new mechanism for handling bit flags. Instead of using an int (or two, or three) to write bits into, this uses the std::bitset in a wrapper class that accepts an enum class as input. This means that certain classes of errors we've had a few of in the engine, where a coder used the wrong set of flags or checked them against the wrong variable (SF_STEALTH vs SIF_STEALTH, for example) can now be detected at a compiler level rather than not at all.
This allows to use standard TrueType Fonts for text rendering in FSO. It uses the NanoVG library which provides the ability of drawing 2D shapes. This library is used for most 2D operations now and can also be used directly by using the PathRenderer class.
Goober5000