update documentation for TR interface

(interface change for distributions, introduced variate_generator)


[SVN r20500]

libs/random

@@ -1 +1 @@
-Subproject commit 9f562428c7e2d2c27e56219987a2857449476c7f
+Subproject commit 340de0df1411cf496126ecd1fa1e9235073c81b5