Export of internal Abseil changes.

--
2dcf3ec79f961d2962cdad33ac4bfbcb14126dad by Abseil Team <absl-team@google.com>:

Consolidate implementations of CountLeadingZeros and add new ones for
CountTrailingZeros.
Internal APIs only.

PiperOrigin-RevId: 209961247

--
4f3ac87c6928dab26faff962bb18aade9383f184 by Jorg Brown <jorg@google.com>:

Fix absl::CUnescape not to write to const_cast<char*>(str->data()), which does the wrong thing if the string type is copy-on-write

PiperOrigin-RevId: 209957656

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c5103067be19dc88a4c32e5306154e5e3bba4673 by Tom Manshreck <shreck@google.com>:

Update comments in time library header files.

PiperOrigin-RevId: 209829588

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fe36f9b6150243d2ac88e2a892d84c565c18cd2f by Abseil Team <absl-team@google.com>:

Clarifying the sample use of absl::LoadTimeZone function in the documentation.

PiperOrigin-RevId: 209782218
GitOrigin-RevId: 2dcf3ec79f961d2962cdad33ac4bfbcb14126dad
Change-Id: I3e2f87a8c543599b81eada58409a9bddc0b51ab8

absl/strings/BUILD.bazel

@@ -70,6 +70,7 @@ cc_library(
     deps = [
         ":internal",
         "//absl/base",
+        "//absl/base:bits",
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:endian",
@@ -87,7 +88,6 @@ cc_library(
         "internal/utf8.cc",
     ],
     hdrs = [
-        "internal/bits.h",
         "internal/char_map.h",
         "internal/ostringstream.h",
         "internal/resize_uninitialized.h",