5.3 libidn and old iconv
5.4 AIX shared build with c-ares fails
5.5 can't handle Unicode arguments in Windows
+ 5.6 Improper use of Autoconf cache variables
6. Authentication
6.1 NTLM authentication and unicode
https://curl.haxx.se/bug/?i=345
https://curl.haxx.se/bug/?i=731
+5.6 Improper use of Autoconf cache variables
+
+ A number of macros used in curl's configure modify the Autoconf cache
+ variables which breaks configure variable caching.
+
+ Issue: https://github.com/curl/curl/issues/603
+
6. Authentication