According to the OpenGL 2.x spec, some calls will set the current
global error to `GL_INVALID_OPERATION` if they are used during
a `glBegin`/`glEnd` block.
This implements `glGetError` and correctly sets the state machine's
error macro (similar to LibC `errno`) when an invalid operation is
performed. This is reset on completion of a successful operation.
This currently (obviously) doesn't support any actual 3D hardware,
hence all calls are done via software rendering.
Note that any modern constructs such as shaders are unsupported,
as this driver only implements Fixed Function Pipeline functionality.
The library is split into a base GLContext interface and a software
based renderer implementation of said interface. The global glXXX
functions serve as an OpenGL compatible c-style interface to the
currently bound context instance.
Co-authored-by: Stephan Unverwerth <s.unverwerth@gmx.de>
