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/adb/sysdeps_unix.cpp b/adb/sysdeps_unix.cpp
index 4445a44..3fdc917 100644
--- a/adb/sysdeps_unix.cpp
+++ b/adb/sysdeps_unix.cpp
@@ -16,7 +16,7 @@
 
 #include "sysdeps.h"
 
-bool set_tcp_keepalive(int fd, int interval_sec) {
+bool set_tcp_keepalive(borrowed_fd fd, int interval_sec) {
     int enable = (interval_sec > 0);
     if (adb_setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &enable, sizeof(enable))) {
         return false;