Add tests checking that ::testing::MockFunction template argument can
be deduced in a function call context. This is a property raised in the
review, however, not checked before by any tests.
gmock-spec-builders.h uses std::function (in MockFunction) but did
not include <functional> to provide it. Apparently, it worked since
the header must have been included by something else but better be
safe than sorry.
Adam Badura