Increase max/min frame range to over a million

For some specific pipelines (e.g., holographic rendering) you can easily
need over a million frames (1k * 1k view angles).

It seems a corner case, but there is no real reason not to allow users
doing that.

That said we do loose subframe precision in the highest frame range. Which can
affect motionblur. The current maximum sub-frame precision we have is 16.
While the previous limit of 500k frames has a precision of 32.

Thanks to Campbell Barton for the help here.

To be backported to 2.79

source/blender/makesdna/DNA_scene_types.h

@@ -1935,16 +1935,18 @@ extern const char *RE_engine_id_CYCLES;
 /* **************** SCENE ********************* */
 
 /* note that much higher maxframes give imprecise sub-frames, see: T46859 */
+/* Current precision is 16 for the sub-frames closer to MAXFRAME. */
+
 /* for general use */
-#define MAXFRAME	500000
-#define MAXFRAMEF	500000.0f
+#define MAXFRAME	1048574
+#define MAXFRAMEF	1048574.0f
 
 #define MINFRAME	0
 #define MINFRAMEF	0.0f
 
 /* (minimum frame number for current-frame) */
-#define MINAFRAME	-500000
-#define MINAFRAMEF	-500000.0f
+#define MINAFRAME	-1048574
+#define MINAFRAMEF	-1048574.0f
 
 /* depricate this! */
 #define TESTBASE(v3d, base)  (                                                \