syscall: Add sys_gettid helper

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

include/syscall-codes.h

@@ -27,6 +27,7 @@
 #define __NR__sysctl		156
 #define __NR_prctl		157
 #define __NR_arch_prctl		158
+#define __NR_gettid		186
 #define __NR_futex		202
 #define __NR_set_thread_area	205
 #define __NR_get_thread_area	211

include/syscall.h

@@ -208,6 +208,11 @@ static always_inline unsigned long sys_getpid(void)
 	return syscall0(__NR_getpid);
 }
 
+static always_inline unsigned long sys_gettid(void)
+{
+	return syscall0(__NR_gettid);
+}
+
 static always_inline long sys_unlink(char *pathname)
 {
 	return syscall1(__NR_unlink, (unsigned long)pathname);