stub mlock and mlockall

No plans in sight to page out anonymous memory, so for now, stub this.
We may have to revisit this once we support proper mmap semantics, specially
with ranged mlock/munlock

runtime.cc

@@ -169,6 +169,16 @@ tdep_get_elf_image (struct elf_image *ei, pid_t pid, unw_word_t ip,
     return 0;
 }
 
+int mlockall(int flags)
+{
+    return 0;
+}
+
+int munlockall(void)
+{
+    return 0;
+}
+
 int getpid()
 {
     return 0;