randomseries [FIX]: add usage information on rng type selection

src/synt/misc/randomseries.cc

@@ -53,7 +53,7 @@ int main(int iargc, char* argv[])
   char usage_text[]=
   {
     RANDOMSERIES_VERSION "\n"
-    "usage: randomseries filename [-v] [-t type] [-o]" "\n"
+    "usage: randomseries filename [-v] [-rngtype t] [-t type] [-o]" "\n"
     "                    [-nseries n] [-nsamples n] [-dt v]" "\n"
     "                    [-std v] [-mean v] [-seed n]" "\n"
     "   or: randomseries --help|-h" "\n"
@@ -75,6 +75,10 @@ int main(int iargc, char* argv[])
     "filename     name of output file\n"
     "-v           be verbose\n"
     "-o           overwrite existing output file\n"
+    "-rngtype t   select random number generator type\n"
+    "             run\n"
+    "               randomseries -xhelp=gslrng\n"
+    "             to see comments\n"
     "-t type      select output file type\n"
     "-nseries n   produce 'n' time series\n"
     "-nsamples n  produce 'n' samples per series\n"