Define sockaddr_storage in bionic

Bionic currently renames the kernel's __kernel_sockaddr_storage
to sockaddr_storage.  We would like to reuse the bionic kernel
headers for musl, but musl defines its own sockaddr_storage,
causing redefinition errors when the musl and kernel headers
are both included.

Give bionic its own definition of sockaddr_storage so the kernel
one can be left as __kernel_sockaddr_storage, avoiding the
conflict in musl.

Some of the structs in netinet/in.h contain sockaddr_storage members.
There are definitions in linux/in.h, but they now use the
__kernel_sockaddr_storage naming.  To avoid having to copy the structs
from linux/in.h into netinet/in.h, add some #define hackery to
rename __kernel_sockaddr_storage to sockaddr_storage when including
linux/in.h from netinet/in.h.

Bug: 190084016
Test: m checkbuild
Test: bionic-unit-tests
Change-Id: I8f654511722b3a4a8e0bb146e4418ebcd370305c
diff --git a/libc/kernel/uapi/linux/socket.h b/libc/kernel/uapi/linux/socket.h
index 608d31f..7ce5304 100644
--- a/libc/kernel/uapi/linux/socket.h
+++ b/libc/kernel/uapi/linux/socket.h
@@ -20,7 +20,7 @@
 #define _UAPI_LINUX_SOCKET_H
 #define _K_SS_MAXSIZE 128
 typedef unsigned short __kernel_sa_family_t;
-struct sockaddr_storage {
+struct __kernel_sockaddr_storage {
   union {
     struct {
       __kernel_sa_family_t ss_family;