Introduce netd_client, a dynamic library that talks to netd.

The library exists outside bionic. It is dynamically loaded, to replace selected
standard socket syscalls with versions that talk to netd.

Change connect() to use the library if available.

(cherry picked from commit 3a6b627a14df8111b03e452f2df4b5f4938e0e49)

Change-Id: Ib6198e19dbc306521a26fcecfdf6e8424d163fc9
diff --git a/libc/arch-arm64/syscalls/connect.S b/libc/arch-arm64/syscalls/__connect.S
similarity index 88%
rename from libc/arch-arm64/syscalls/connect.S
rename to libc/arch-arm64/syscalls/__connect.S
index d3cd43d..c46f418 100644
--- a/libc/arch-arm64/syscalls/connect.S
+++ b/libc/arch-arm64/syscalls/__connect.S
@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(connect)
+ENTRY(__connect)
     stp     x29, x30, [sp, #-16]!
     mov     x29,  sp
     str     x8,       [sp, #-16]!
@@ -18,4 +18,5 @@
     b.hi    __set_errno
 
     ret
-END(connect)
+END(__connect)
+.hidden __connect