shrink huge gethostbyname buffer

careful analysis has shown that the buffer is only ever used for
at most a single hostname, so 256 bytes are sufficient.
the huge 8KB buffer caused stack overflow when used with microsocks,
which defaults to tiny thread stacks of 8KB with musl libc.

src/core.h

@@ -117,7 +117,7 @@ struct gethostbyname_data {
 	struct hostent hostent_space;
 	in_addr_t resolved_addr;
 	char *resolved_addr_p[2];
-	char addr_name[1024 * 8];
+	char addr_name[256];
 };
 
 struct hostent* proxy_gethostbyname(const char *name, struct gethostbyname_data *data);