random: Add __gnu_cxx::beta_distribution<> class.

	* libstdc++-v3/include/ext/random: Add __gnu_cxx::beta_distribution<>
	class.
	* libstdc++-v3/include/ext/random.tcc: Add out-of-line functions for
	__gnu_cxx::beta_distribution<>.
	* libstdc++-v3/testsuite/26_numerics/random/beta_distribution/
	operators/equal.cc: New file.
	* libstdc++-v3/testsuite/26_numerics/random/beta_distribution/
	operators/serialize.cc: New file.
	* libstdc++-v3/testsuite/26_numerics/random/beta_distribution/
	operators/inequal.cc: New file.
	* libstdc++-v3/testsuite/26_numerics/random/beta_distribution/
	cons/parms.cc: New file.
	* libstdc++-v3/testsuite/26_numerics/random/beta_distribution/
	cons/default.cc: New file.
	* libstdc++-v3/testsuite/26_numerics/random/beta_distribution/
	requirements/typedefs.cc: New file.
	* libstdc++-v3/testsuite/26_numerics/random/beta_distribution/
	requirements/explicit_instantiation/1.cc: New file.

From-SVN: r190954