Add some platform abstractions.

(This is a merge of http://go/wvgerrit/70303)

This adds a platform.h file to abstract some of the differences
between Windows and POSIX platforms.  This includes ntohl, setenv,
and ssize_t.

Bug: 122953649
Test: Android Unit Tests
Change-Id: I3235f3f284b53d24d7365ff3f4a06dcd9b403697

libwvdrmengine/cdm/core/test/buffer_reader_test.cpp

@@ -4,7 +4,6 @@
 
 #include <string>
 #include <errno.h>
-#include <getopt.h>
 #include <gtest/gtest.h>
 
 #include "buffer_reader.h"

libwvdrmengine/cdm/core/test/crypto_session_unittest.cpp

@@ -2,7 +2,6 @@
 // source code may only be used and distributed under the Widevine Master
 // License Agreement.
 
-#include <arpa/inet.h>
 #include <memory>
 #include <string>
 
@@ -13,6 +12,7 @@
 #include "key_session.h"
 #include "license_protocol.pb.h"
 #include "log.h"
+#include "platform.h"
 #include "metrics.pb.h"
 #include "metrics_collections.h"
 #include "test_base.h"

libwvdrmengine/cdm/core/test/generic_crypto_unittest.cpp

@@ -7,7 +7,6 @@
 // This is because we need a valid RSA certificate, and will attempt to connect
 // to the provisioning server to request one if we don't.
 
-#include <arpa/inet.h>
 #include <gtest/gtest.h>
 #include <memory>
 #include <string>
@@ -19,6 +18,7 @@
 #include "oec_session_util.h"
 #include "oemcrypto_session_tests_helper.h"
 #include "oemcrypto_types.h"
+#include "platform.h"
 #include "properties.h"
 #include "string_conversions.h"
 #include "test_base.h"

libwvdrmengine/cdm/core/test/initialization_data_unittest.cpp

@@ -2,13 +2,13 @@
 // source code may only be used and distributed under the Widevine Master
 // License Agreement.
 
-#include <arpa/inet.h>
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
 #include "file_store.h"
 #include "initialization_data.h"
 #include "license_protocol.pb.h"
+#include "platform.h"
 #include "string_conversions.h"
 #include "wv_cdm_constants.h"
 

libwvdrmengine/cdm/core/test/test_base.cpp

@@ -21,6 +21,7 @@
 #include "log.h"
 #include "oec_device_features.h"
 #include "oec_test_data.h"
+#include "platform.h"
 #include "properties.h"
 #include "test_printers.h"
 #include "url_request.h"