Mark sockets on creation (socket()) and accept4().

Remove the separate syscall for accept() and implement it as accept4(..., 0).

Change-Id: Ib0b8f5d7c5013b91eae6bbc3847852eb355c7714
diff --git a/libc/Android.mk b/libc/Android.mk
index f0ee09d..caf0bac 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -98,6 +98,7 @@
 libc_bionic_src_files := \
     bionic/abort.cpp \
     bionic/accept.cpp \
+    bionic/accept4.cpp \
     bionic/access.cpp \
     bionic/assert.cpp \
     bionic/atof.cpp \
@@ -199,6 +200,7 @@
     bionic/sigprocmask.cpp \
     bionic/sigsuspend.cpp \
     bionic/sigwait.cpp \
+    bionic/socket.cpp \
     bionic/stat.cpp \
     bionic/statvfs.cpp \
     bionic/strerror.cpp \