Add new std::basic_string constructor (LWG 2583)
* config/abi/pre/gnu.ver (GLIBCXX_3.4, GLIBCXX_3.4.21): Use more
precise patterns for basic_string constructors.
(GLIBCXX_3.4.23): Export new constructors.
* doc/xml/manual/intro.xml: Document LWG 2583 status.
* doc/html/*: Regenerate.
* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
(basic_string(const basic_string&, size_type, const Alloc&)): Add
new constructor for LWG 2583.
(basic_string(const basic_string&, size_type, size_type)): Remove
default argument.
[!_GLIBCXX_USE_CXX11_ABI]: Likewise.
* include/bits/basic_string.tcc [!_GLIBCXX_USE_CXX11_ABI]: Define it.
* testsuite/21_strings/basic_string/cons/char/8.cc: New test.
* testsuite/21_strings/basic_string/cons/wchar_t/8.cc: New test.
From-SVN: r239773
86bbf15b6b