target-supports.exp (check_iconv_available): Default libiconv to -liconv, if there...

target-supports.exp (check_iconv_available): Default libiconv to -liconv, if there is no definition.

	* lib/target-supports.exp (check_iconv_available): Default
	libiconv to -liconv, if there is no definition.

	* testsuite/lib/libstdc++.exp (libstdc++_init): Improve handling
	of compilers not in the build directory.
	(libstdc++_wchar_t): New variable.
	(libstdc++_threads): Likewise.
	(libstdc++_test_objs): Likewise.
	(v3_target_compile): Use libstdc++_test_objs.
	(v3-list-tests): Remove.
	(listdc++_build_support): New function.
	* testsuite/libstdc++-dg/normal.exp: Rework to dynamically
	generate list of tests.

From-SVN: r96934