Googletest export

Explicitly define copy constructors used in googletest tests

As of C++11, providing a user-declared copy assignment operator should
suppress the availability of an implicit default copy constructor.
Classes that provide (or delete) a copy assignment operator must provide
their own copy constructor if one is desired. This may be an explicit
default copy constructor if appropriate.

As googletest is a C++11 codebase, this change should be made without
qualification.

This addresses the -Wdeprecated-copy warnings issued by trunk clang:

While compiling googletest/test/googletest-death-test-test.cc:

In file included from .../googletest/test/googletest-death-test-test.cc:33:
.../googletest/include/gtest/gtest-death-test.h:196:8: error: definition of implicit copy constructor for 'ExitedWithCode' is deprecated because it has a user-declared copy assignment operator [-Werror,-Wdeprecated-copy]
  void operator=(const ExitedWithCode& other);
       ^
.../googletest/test/googletest-death-test-test.cc:279:16: note: in implicit copy constructor for 'testing::ExitedWithCode' first required here
  EXPECT_PRED1(pred0,  status0);
               ^

While compiling googletest/test/googletest-param-test-test.cc:

.../googletest/test/googletest-param-test-test.cc:502:8: error: definition of implicit copy constructor for 'NonDefaultConstructAssignString' is deprecated because it has a user-declared copy assignment operator [-Werror,-Wdeprecated-copy]
  void operator=(const NonDefaultConstructAssignString&);
       ^
.../googletest/test/googletest-param-test-test.cc:507:36: note: in implicit copy constructor for 'NonDefaultConstructAssignString' first required here
      Combine(Values(0, 1), Values(NonDefaultConstructAssignString("A"),

This matches other changes made elsewhere in the googletest codebase,
such as 306f3754. Perhaps those previous changes did not consider
test code.

PiperOrigin-RevId: 307495126