Hide accidentally-exposed __clock_nanosleep.

Bug: http://b/21858067
Change-Id: Iaa83a5e17cfff796aed4f641d0d14427614d9399
diff --git a/libc/arch-x86/syscalls/__clock_nanosleep.S b/libc/arch-x86/syscalls/___clock_nanosleep.S
similarity index 90%
rename from libc/arch-x86/syscalls/__clock_nanosleep.S
rename to libc/arch-x86/syscalls/___clock_nanosleep.S
index 75a54d1..088a92e 100644
--- a/libc/arch-x86/syscalls/__clock_nanosleep.S
+++ b/libc/arch-x86/syscalls/___clock_nanosleep.S
@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(__clock_nanosleep)
+ENTRY(___clock_nanosleep)
     pushl   %ebx
     .cfi_def_cfa_offset 8
     .cfi_rel_offset ebx, 0
@@ -33,4 +33,5 @@
     popl    %ecx
     popl    %ebx
     ret
-END(__clock_nanosleep)
+END(___clock_nanosleep)
+.hidden ___clock_nanosleep