Getting rid of setlinestyle: non-camera 3DView render border.

Also fixed wrong color for in-camera render border, and added a comment
to imm_cpack about expected color components order in integer parameter.

source/blender/gpu/intern/gpu_immediate_util.c

@@ -36,6 +36,8 @@
 /**
 * Pack color into 3 bytes
 *
+* \Note BGR format (i.e. 0xBBGGRR)...
+*
 * \param x color.
 */
 void imm_cpack(unsigned int x)