re PR libstdc++/55047 (operator() in std::exponential_distribution may call log(0))

2012-10-24   Haakan Younes  <hyounes@google.com>
	     Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/55047
	* include/bits/random.h (exponential_distribution<>::operator):
	Fix formula to std::log(result_type(1) - __aurng()).
	* include/bits/random.tcc: Likewise, everywhere.

Co-Authored-By: Paolo Carlini <paolo.carlini@oracle.com>

From-SVN: r192762