Change preprocessor OS tests to __linux__
"linux" without leading underscores is deprecated and less reliable.
diff --git a/nanohttp.c b/nanohttp.c
index b911f9c..0533102 100644
--- a/nanohttp.c
+++ b/nanohttp.c
@@ -1130,7 +1130,7 @@
* extraction code. it work on Linux, if it work on your platform
* and one want to enable it, send me the defined(foobar) needed
*/
-#if defined(HAVE_NETDB_H) && defined(HOST_NOT_FOUND) && defined(linux)
+#if defined(HAVE_NETDB_H) && defined(HOST_NOT_FOUND) && defined(__linux__)
const char *h_err_txt = "";
switch (h_errno) {