libstdc++: Rename test type to avoid clashing with std::any

libstdc++: Rename test type to avoid clashing with std::any

When PCH are enabled this test file includes <any> and so the
using-directive brings std::any into the global scope. It isn't
currently a problem, because the -std option in the dg-options means
that PCH is not used. If that option is removed, the test fails with PCH
and passes without.

This just renames the type to avoid the name classh (and also the 'none'
type for consistency).

libstdc++-v3/ChangeLog:

	* testsuite/20_util/variant/compile.cc: Rename 'any' to avoid
	clash with std::any.