for a variate_generator, use a base_generator_type *reference*

(otherwise, a copy is made)


[SVN r28794]

libs/random

@@ -1 +1 @@
-Subproject commit a3e3daf57915cbdb576a8bb025740cfd93cf5e87
+Subproject commit 7c758f70fc29ecc50ea2e062ac454b93112a9646