winsys/intel: keep drm_intel_decode around

And send the results to stderr, in line with debug_error()/debug_printf().
i965g: winsys is owned by screen
i965g: move I965_MAX_* to i965_context.h
i965g: add functions for logging/dumping
i965g: switch to i965's printf()
i965g: keep I965_DEBUG for release builds
i965g: remove i965_warn() from tc_fail()
i965g: treat compilation failures as bugs