Add recvmmsg and sendmmsg syscalls.

Also add the corresponding constant, struct, and function declarations
to <sys/socket.h>, and perfunctory tests so we know that the symbols
actually exist.

Signed-off-by: Guillaume Ranquet <guillaumex.ranquet@intel.com>
Change-Id: Ib0d854239d3716be90ad70973c579aff4895a4f7
diff --git a/tests/Android.mk b/tests/Android.mk
index 5fafba6..451b3a9 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -71,6 +71,7 @@
     sys_resource_test.cpp \
     sys_select_test.cpp \
     sys_sendfile_test.cpp \
+    sys_socket_test.cpp \
     sys_stat_test.cpp \
     sys_statvfs_test.cpp \
     sys_syscall_test.cpp \