Avoid memory leak in case realloc fails. Simplification for
better code generation.
Avoid deprecation warning because of libc_hidden_proto for
inet6_option_alloc.
* inet/inet6_option.c (option_alloc): Renamed from
inet6_option_alloc. Made static.
(inet6_option_alloc): New a simple wrapper around option_alloc.
(inet6_option_append): Call option_alloc.
* include/netinet/in.h: Remove libc_hidden_proto for
inet6_option_alloc.