Export of internal Abseil changes.

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ed4be0cb9a708158187a0628c1c2167ae6783274 by Greg Falcon <gfalcon@google.com>:

Refactor a string unit test into a template function for internal purposes.

PiperOrigin-RevId: 210798880

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e4c734be903ac7b3a88caf4b17909343c283a21a by Abseil Team <absl-team@google.com>:

Add a note that the RFC3339_* format specifiers use %Y, and so
do not produce 4-digit years on output nor require 4-digit years
on input, as a strict reading of RFC3339 might require.

PiperOrigin-RevId: 210785544

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cfb5e32f9397e49ddb731445a191b36652fe2f6d by Greg Falcon <gfalcon@google.com>:

Refactor a string unit test into a template function for internal purposes.

PiperOrigin-RevId: 210776525

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105ee700e62869cfda2a37e6f7c2ea483f8fc75e by Xiaoyi Zhang <zhangxy@google.com>:

Correctly define ABSL_HAVE_STD_STRING_VIEW for MSVC 2017. Currently the macro
is not defined even though MSVC 2017 provides `std::string_view`, and this
means both `absl::string_view` and `std::string_view` exist as distinct types.
A bunch of places relying on the false assumption that
`string_view::const_iterator` is `const char*` have to be fixed to build
successfully.

See related github issue https://github.com/abseil/abseil-cpp/issues/161.

PiperOrigin-RevId: 210764947
GitOrigin-RevId: ed4be0cb9a708158187a0628c1c2167ae6783274
Change-Id: I7a9658b3201aa669db9d3d90474feb08072718c7

absl/strings/str_split_test.cc

@@ -763,7 +763,7 @@ template <typename Delimiter>
 static bool IsFoundAtStartingPos(absl::string_view text, Delimiter d,
                                  size_t starting_pos, int expected_pos) {
   absl::string_view found = d.Find(text, starting_pos);
-  return found.data() != text.end() &&
+  return found.data() != text.data() + text.size() &&
          expected_pos == found.data() - text.data();
 }