fix number of maximum number of parameters

CUDA/options/options.h

 #define MAXNFIBRES 4 
-#define MAXNPARAMS 15
-//NFIBRES*3 + S0 + d + d_std + f0 + rician = 15
+#define MAXNPARAMS 16
+//MAXNFIBRES*3 + S0 + d + d_std + f0 = 16
+//rician only in runmcmc and doesn't use MAXNPARAMS
 #define MAXNDIR 640
 //640 gradient directions
 #define THREADS_BLOCK_MCMC 64