[libcxx] Fix memory leak in strstream tests.

[EricWF]

Summary

The strstream function str() sets freeze(true). When freeze is true the destructor is not allowed to free any dynamically allocated memory. The memory leak causes ASAN to fail on these tests. To ensure memory is deallocated strstream.freeze(false) is called at the end of the tests.

[mclow.lists]

What an ugly, leak-prone API. No wonder we deprecated it.

[mclow.lists]

I would love to see a better way to solve this; however, I don't see one, given the specification for strstream

test/depr/depr.str.strstreams/depr.ostrstream/depr.ostrstream.cons/default.pass.cpp

     std::string s("dog");
     out << i << ' ' << d << ' ' << s << std::ends;
     assert(out.str() == std::string("123 4.5 dog"));
+    out.freeze(false);
 }

test/depr/depr.str.strstreams/depr.ostrstream/depr.ostrstream.members/freeze.pass.cpp

         out << 'a';
         out << char(0);
         assert(out.str() == std::string("a"));
+        out.freeze(false);
     }
 }

test/depr/depr.str.strstreams/depr.ostrstream/depr.ostrstream.members/str.pass.cpp

         std::ostrstream out;
         out << 123 << ' ' << 4.5 << ' ' << "dog" << std::ends;
         assert(out.str() == std::string("123 4.5 dog"));
+        out.freeze(false);
     }
 }

test/depr/depr.str.strstreams/depr.strstream/depr.strstream.cons/default.pass.cpp

     assert(i == 123);
     assert(d == 4.5);
     assert(strcmp(s.c_str(), "dog") == 0);
+    inout.freeze(false);
 }

test/depr/depr.str.strstreams/depr.strstream/depr.strstream.oper/freeze.pass.cpp

         out << 'a';
         out << char(0);
         assert(out.str() == std::string("a"));
+        out.freeze(false);
     }
 }

test/depr/depr.str.strstreams/depr.strstream/depr.strstream.oper/str.pass.cpp

         std::strstream out;
         out << 123 << ' ' << 4.5 << ' ' << "dog" << std::ends;
         assert(out.str() == std::string("123 4.5 dog"));
+        out.freeze(false);
     }
 }

test/depr/depr.str.strstreams/depr.strstreambuf/depr.strstreambuf.members/pcount.pass.cpp

         assert(sb.pcount() == 2);
         assert(sb.str() == std::string("a"));
         assert(sb.pcount() == 2);
+        sb.freeze(false);
     }
 }

test/depr/depr.str.strstreams/depr.strstreambuf/depr.strstreambuf.members/str.pass.cpp

         assert(sb.sputc('a') == 'a');
         assert(sb.sputc(0) == 0);
         assert(sb.str() == std::string("a"));
+        sb.freeze(false);
     }
 }