poly1305/asm/poly1305-x86_64.pl: contain symbols within shared lib.

We don't need it, but external users might find it handy.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

crypto/poly1305/asm/poly1305-x86_64.pl

@@ -130,8 +130,12 @@ $code.=<<___;
 .extern	OPENSSL_ia32cap_P
 
 .globl	poly1305_init
+.hidden	poly1305_init
 .globl	poly1305_blocks
+.hidden	poly1305_blocks
 .globl	poly1305_emit
+.hidden	poly1305_emit
+
 .type	poly1305_init,\@function,3
 .align	32
 poly1305_init: