Revert "Revert "Add a way to turn off unique_fd's operator int.""

The original commit broke aosp-master-with-phones, because of
vendor libraries the depended on the int versions of libbase functions.

This patch reverts the revert, and also adds ABI-compatibility shims for
the replaced functions.

This reverts commit 2c58e1924a7bf1b44049764fddb40c1704dc288f.

Bug: http://b/131312539
Test: treehugger
Test: forrest run of aosp-master-with-phones
Change-Id: I75cc84ec8d963e20862f7662e8e2f409471f41cc
diff --git a/base/Android.bp b/base/Android.bp
index 38f301a..9be49ad7 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -45,6 +45,7 @@
     name: "libbase_defaults",
     defaults: ["libbase_cflags_defaults"],
     srcs: [
+        "abi_compatibility.cpp",
         "chrono_utils.cpp",
         "cmsg.cpp",
         "file.cpp",