Do define some IPv6 related symbols even with IPv6 disabled. Fixes compilation of some faulty applictions.

--- libc/sysdeps/linux/common/bits/in.h
+++ libc/sysdeps/linux/common/bits/in.h
@@ -103,7 +103,7 @@
     struct in_addr ipi_addr;		/* Header destination address  */
   };
 
-#ifdef __UCLIBC_HAS_IPV6__
+#if defined __UCLIBC_HAS_IPV6__ || !defined __UCLIBC_STRICT_HEADERS__
 /* Options for use with `getsockopt' and `setsockopt' at the IPv6 level.
    The first word in the comment at the right is the data type used;
    "bool" means a boolean value stored in an `int'.  */