libc: implement kernel vdso syscalls for i386

This patch uses __kernel_vsyscall instead of "int 0x80"
as the syscall entry point. AT_SYSINFO points to
an adapter to mask the arch specific difference and gives a
performance boost on i386 architecture.

Change-ID: Ib340c604d02c6c25714a95793737e3cfdc3fc5d7
Signed-off-by: Mingwei Shi <mingwei.shi@intel.com>
diff --git a/libc/bionic/__libc_init_main_thread.cpp b/libc/bionic/__libc_init_main_thread.cpp
index a29d8a7..01bb9bb 100644
--- a/libc/bionic/__libc_init_main_thread.cpp
+++ b/libc/bionic/__libc_init_main_thread.cpp
@@ -51,6 +51,9 @@
 
 void __libc_init_main_thread(KernelArgumentBlock& args) {
   __libc_auxv = args.auxv;
+#if defined(__i386__)
+  __libc_init_sysinfo(args);
+#endif
 
   static pthread_internal_t main_thread;