basic_string.h: Use noexcept per the FDIS (minus compare(const string&)...

basic_string.h: Use noexcept per the FDIS (minus compare(const string&)...

2011-05-31  Paolo Carlini  <paolo.carlini@oracle.com>

	* include/bits/basic_string.h: Use noexcept per the FDIS (minus
	compare(const string&), which uses char_traits::compare, which
	isn't noexcept; also no noexcept in the move assignment operator
	and move assign, see c++std-lib-30855).
	* include/bits/basic_string.tcc: Likewise.
	* include/ext/vstring.h: Likewise.
	* include/ext/vstring.tcc: Likewise.
	* include/debug/string: Likewise.

From-SVN: r174479