PR c++/5287, PR c++/7910,  PR c++/11021
	* testsuite/g++.dg/ext/dllimport1.C: Add mingw32 as target. Add
	tests for warnings.
	* testsuite/g++.dg/ext/dllimport2.C: Add tests for warnings.
	* testsuite/g++.dg/ext/dllimport3.C: Likewise.
	* testsuite/g++.dg/ext/dllimport4.C: New file.
	* testsuite/g++.dg/ext/dllimport5.C: New file.
	* testsuite/g++.dg/ext/dllimport6.C: New file.
	* testsuite/g++.dg/ext/dllimport7.C: New file.
	* testsuite/g++.dg/ext/dllimport8.C: New file.
	* testsuite/g++.dg/ext/dllimport9.C: New file.
	* testsuite/g++.dg/ext/dllimport10.C: New file.
	* testsuite/g++.dg/ext/dllexport1.C: New file.

From-SVN: r68917