2012-04-14  Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/52699
	* include/bits/random.tcc (independent_bits_engine<>::operator()())
	Avoid various overflows; use common_type on result_type and
	_RandomNumberEngine::result_type; avoid floating point computations;
	other smaller tweaks.

	* include/bits/random.tcc (uniform_int_distribution<>::operator())
	Use common_type; assume _UniformRandomNumberGenerator::result_type
	unsigned; tidy.

	* include/bits/stl_algobase.h (__lg(unsigned), __lg(unsigned long),
	__lg(unsigned long long)): Add.

From-SVN: r186456