automatic detenction of texture mode and batching based on it

src/textures/modes.h

@@ -0,0 +1,11 @@
+#ifndef TEXTURES_MODES_H
+#define TEXTURES_MODES_H
+
+/* alpha channel information */
+enum texture_mode {
+	TEXTURE_MODE_OPAQUE, 		/* all pixels are solid */
+	TEXTURE_MODE_SEETHROUGH,	/* some pixels are alpha zero */
+	TEXTURE_MODE_GHOSTLY,		/* arbitrary alpha values */
+};
+
+#endif