PR libstdc++/67578 Implement non-trivial std::random_device::entropy

PR libstdc++/67578 Implement non-trivial std::random_device::entropy

2017-05-23  Xi Ruoyao  <ryxi@stu.xidian.edu.cn>
	    Jonathan Wakely  <jwakely@redhat.com>

	PR libstdc++/67578
	* acinclude.m4: Bump libtool_VERSION.
	* config/abi/pre/gnu.ver: Create GLIBCXX_3.4.24 with new symbol.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Add test for <linux/random.h>.
	* doc/xml/manual/abi.xml: Document new library version.
	* include/bits/random.h (random_device::entropy)
	[_GLIBCXX_USE_RANDOM_TR1]: Add call to new _M_getentropy member.
	(random_device::_M_getentropy): Declare.
	* src/c++11/random.cc (random_device::_M_getentropy): Define.
	* testsuite/util/testsuite_abi.cc: Add GLIBCXX_3.4.24 to known
	versions, and make it the latest version.

Co-Authored-By: Jonathan Wakely <jwakely@redhat.com>
From-SVN: r248374