Use __predict_false on some fortify methods.

Give the compiler some hints that these error conditions
are unlikely to occur in practice.

Change-Id: Ifaf7322a12120ef663c8315c1a18c2dcbe4bda23

libc/bionic/__strncpy_chk.cpp

@@ -44,7 +44,7 @@
 extern "C" char *__strncpy_chk (char *dest, const char *src,
               size_t len, size_t dest_len)
 {
-    if (len > dest_len) {
+    if (__predict_false(len > dest_len)) {
         __fortify_chk_fail("strncpy buffer overflow",
                              BIONIC_EVENT_STRNCPY_BUFFER_OVERFLOW);
     }