Export of internal Abseil changes

--
4503a1945d61540d3f7dd9ee2399297fbd423b82 by Andy Soffer <asoffer@google.com>:

Releasing absl::MockingBitGen and absl::BitGenRef

PiperOrigin-RevId: 281594380

--
2cb926fd9e39b5fa24c9541bfafcf18916cf7df2 by Abseil Team <absl-team@google.com>:

Explicitly export files needed by other packages

PiperOrigin-RevId: 281482304
GitOrigin-RevId: 4503a1945d61540d3f7dd9ee2399297fbd423b82
Change-Id: Id9f694eaaa23f42de817c8e8a28e6f86444f5637

absl/random/mocking_bit_gen.cc

@@ -0,0 +1,28 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+#include "absl/random/mocking_bit_gen.h"
+
+#include <string>
+
+namespace absl {
+MockingBitGen::~MockingBitGen() {
+
+  for (const auto& del : deleters_) {
+    del();
+  }
+}
+
+}  // namespace absl