Add interfaces to retrieve random numbers in bulk.

Add interfaces to retrieve random numbers in bulk.

	* include/bits/random.h (uniform_int_distribution<>): Add __generate
	and __generate_impl functions.
	(uniform_real_distribution<>): Likewise.
	(bernoulli_distribution): Likewise.
	(geometric_distribution<>): Likewise.
	(negative_binomial_distribution<>): Likewise.
	(poisson_distribution<>): Likewise.
	(exponential_distribution<>): Likewise.
	(normal_distribution<>): Likewise.
	(lognormal_distribution<>): Likewise.
	(chi_squared_distribution<>): Likewise.
	(cauchy_distribution<>): Likewise.
	(fisher_f_distribution<>): Likewise.
	(student_t_distribution<>): Likewise.
	(gamma_distribution<>): Likewise.
	(weibull_distribution<>): Likewise.
	(extreme_value_distribution<>): Likewise.
	(discrete_distribution<>): Likewise.
	(piecewise_constant_distribution<>): Likewise.
	(piecewise_linear_distribution<>): Likewise.
	* include/bits/random.tcc (__detail::_Power_of_2): New function.
	(uniform_int_distribution<>::__generate_impl): New function.
	(uniform_real_distribution<>::__generate_impl): New function.
	(bernoulli_distribution::__generate_impl): New function.
	(geometric_distribution<>::__generate_impl): New function.
	(negative_binomial_distribution<>::__generate_impl): New function.
	(poisson_distribution<>::__generate_impl): New function.
	(exponential_distribution<>::__generate_impl): New function.
	(normal_distribution<>::__generate_impl): New function.
	(lognormal_distribution<>::__generate_impl): New function.
	(chi_squared_distribution<>::__generate_impl): New function.
	(cauchy_distribution<>::__generate_impl): New function.
	(fisher_f_distribution<>::__generate_impl): New function.
	(student_t_distribution<>::__generate_impl): New function.
	(gamma_distribution<>::__generate_impl): New function.
	(weibull_distribution<>::__generate_impl): New function.
	(extreme_value_distribution<>::__generate_impl): New function.
	(discrete_distribution<>::__generate_impl): New function.
	(piecewise_constant_distribution<>::__generate_impl): New function.
	(piecewise_linear_distribution<>::__generate_impl): New function.

From-SVN: r190712