changed MAX_PSNR to 100

Changing the MAX_PSNR to 100 to allow testing of further experiments
on extending quantizer range to near lossless. With an effective
quantizer of 1, encoder achieves ~68DB, which is consistent with
fdct/idct round trip error.

Change-Id: I7b6d0e94a8936968ef42e82e63ebb13999c36832

vp8/encoder/psnr.c

@@ -13,7 +13,7 @@
 #include "math.h"
 #include "systemdependent.h" /* for vp8_clear_system_state() */
 
-#define MAX_PSNR 60
+#define MAX_PSNR 100
 
 double vp8_mse2psnr(double Samples, double Peak, double Mse)
 {