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/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 93ed85c..e9fb575 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -234,7 +234,7 @@
 int           socket(int, int, int)              arm,arm64,mips,mips64,x86_64
 int           socketpair(int, int, int, int*)    arm,arm64,mips,mips64,x86_64
 int           bind(int, struct sockaddr*, int)  arm,arm64,mips,mips64,x86_64
-int           connect(int, struct sockaddr*, socklen_t)   arm,arm64,mips,mips64,x86_64
+int           __connect:connect(int, struct sockaddr*, socklen_t)   arm,arm64,mips,mips64,x86_64
 int           listen(int, int)                   arm,arm64,mips,mips64,x86_64
 int           accept(int, struct sockaddr*, socklen_t*)  arm,arm64,mips,mips64,x86_64
 int           accept4(int, struct sockaddr*, socklen_t*, int)  arm,arm64,mips,mips64,x86_64
@@ -253,7 +253,7 @@
 # sockets for x86. These are done as an "indexed" call to socketcall syscall.
 int           socket:socketcall:1(int, int, int) x86
 int           bind:socketcall:2(int, struct sockaddr*, int)  x86
-int           connect:socketcall:3(int, struct sockaddr*, socklen_t)   x86
+int           __connect:socketcall:3(int, struct sockaddr*, socklen_t)   x86
 int           listen:socketcall:4(int, int)                   x86
 int           accept:socketcall:5(int, struct sockaddr*, socklen_t*)  x86
 int           getsockname:socketcall:6(int, struct sockaddr*, socklen_t*)  x86