scrypt: raise the maximum GPU intensity for scrypt mining to 31 - benefits shown for AMD R9 290 models

Discussion found here: https://litecointalk.org/index.php/topic,6925.msg54952.html#msg54952

README.scrypt

@@ -43,8 +43,8 @@ setx GPU_USE_SYNC_OBJECTS 1
 --intensity XX (-I XX)
 
 Just like in Bitcoin mining, scrypt mining takes an intensity, however the
-scale goes from 0 to 20 to mimic the "Aggression" used in mtrlt's reaper. The
-reason this is crucial is that too high an intensity can actually be
+scale goes from 0 to 31. 
+The reason this is crucial is that too high an intensity can actually be
 disastrous with scrypt because it CAN run out of ram. High intensities
 start writing over the same ram and it is highly dependent on the GPU, but they
 can start actually DECREASING your hashrate, or even worse, start producing

miner.h

@@ -1075,8 +1075,8 @@ extern bool add_pool_details(struct pool *pool, bool live, char *url, char *user
 #define MAX_SHA_INTENSITY_STR "14"
 #define MIN_SCRYPT_INTENSITY 8
 #define MIN_SCRYPT_INTENSITY_STR "8"
-#define MAX_SCRYPT_INTENSITY 20
-#define MAX_SCRYPT_INTENSITY_STR "20"
+#define MAX_SCRYPT_INTENSITY 31
+#define MAX_SCRYPT_INTENSITY_STR "31"
 #ifdef USE_SCRYPT
 #define MIN_INTENSITY (opt_scrypt ? MIN_SCRYPT_INTENSITY : MIN_SHA_INTENSITY)
 #define MIN_INTENSITY_STR (opt_scrypt ? MIN_SCRYPT_INTENSITY_STR : MIN_SHA_INTENSITY_STR)