[Mesa-dev] EGL: Implement EGL_KHR_debug

[Kyle Brenneman]

This is a set of patches to implement the EGL_KHR_debug extension.

In addition to hopefully being useful in its own right, the current draft of
the libglvnd interface for EGL requires each vendor library to support
EGL_KHR_debug. The same functions should work for both a normal and
libglvnd-based driver.

Rather than try to update every _eglError call all at once, I used the
_EGLThreadInfo struct to record the current function name and object label, so
all the existing _eglError calls will call the debug callback with the correct
command and label. They won't have any error messages with them, but those
messages can be added in later changes.