Defining 'ptr' fails on Solaris because it's used in <netdb.h>.

Including the Filesystem TS header fails if the TS support wasn't
enabled by configure.

	* testsuite/17_intro/names.cc: Do not check 'ptr' on Solaris.
	* testsuite/experimental/names.cc: Include <experimental/filesystem>
	conditionally.

From-SVN: r271421