Remove __overloadable/__RENAME_CLANG

Now that we have a clang that supports transparent overloads, we can
kill all of this cruft, and restore our upstream sources to their
untouched glory. Woohoo!

Bug: 12231437
Test: Built aosp_marlin; no obvious patch-related aosp_mips issues.
Change-Id: I520a19d014f12137f80e43f973dccd6711c571cd
diff --git a/libc/bionic/getcwd.cpp b/libc/bionic/getcwd.cpp
index 50487ec..a8bbcf3 100644
--- a/libc/bionic/getcwd.cpp
+++ b/libc/bionic/getcwd.cpp
@@ -33,7 +33,7 @@
 
 extern "C" int __getcwd(char* buf, size_t size);
 
-char* getcwd(char* buf, size_t size) __overloadable {
+char* getcwd(char* buf, size_t size) {
   // You can't specify size 0 unless you're asking us to allocate for you.
   if (buf != NULL && size == 0) {
     errno = EINVAL;
diff --git a/libc/bionic/poll.cpp b/libc/bionic/poll.cpp
index 1d72fe5..1a54832 100644
--- a/libc/bionic/poll.cpp
+++ b/libc/bionic/poll.cpp
@@ -36,7 +36,7 @@
 extern "C" int __ppoll(pollfd*, unsigned int, timespec*, const sigset64_t*, size_t);
 extern "C" int __pselect6(int, fd_set*, fd_set*, fd_set*, timespec*, void*);
 
-int poll(pollfd* fds, nfds_t fd_count, int ms) __overloadable {
+int poll(pollfd* fds, nfds_t fd_count, int ms) {
   timespec ts;
   timespec* ts_ptr = nullptr;
   if (ms >= 0) {
@@ -46,7 +46,7 @@
   return __ppoll(fds, fd_count, ts_ptr, nullptr, 0);
 }
 
-int ppoll(pollfd* fds, nfds_t fd_count, const timespec* ts, const sigset_t* ss) __overloadable {
+int ppoll(pollfd* fds, nfds_t fd_count, const timespec* ts, const sigset_t* ss) {
   // The underlying `__ppoll` system call only takes `sigset64_t`.
   SigSetConverter set;
   sigset64_t* ss_ptr = nullptr;
diff --git a/libc/bionic/send.cpp b/libc/bionic/send.cpp
index 8f175d3..2e5d457 100644
--- a/libc/bionic/send.cpp
+++ b/libc/bionic/send.cpp
@@ -28,6 +28,6 @@
 
 #include <sys/socket.h>
 
-ssize_t send(int socket, const void* buf, size_t len, int flags) __overloadable {
+ssize_t send(int socket, const void* buf, size_t len, int flags) {
   return sendto(socket, buf, len, flags, NULL, 0);
 }