[Nut-upsuser] ./configure --with-openssl fails with OpenSSL 1.1, SSL_library_init now a macro

[Roger Price]

I was unable to run ./configure --with-openssl on Debian Stretch.  The 
./configure output ends with

   checking for OpenSSL version via pkg-config... 1.1.0f found
   checking for OpenSSL cflags...
   checking for OpenSSL ldflags... -lssl -lcrypto
   checking for openssl/ssl.h... yes
   checking for SSL_library_init... no
   configure: error: "OpenSSL not found, required for SSL support"

The giveaway is that ssl.h which defines SSL_library_init is present, but 
configure can't see the symbol SSL_library_init.

As often happens, the folks over at Arch Linux have the technical details, and 
the explanation is to be found at https://bugs.archlinux.org/task/53809 
[FS#53809 - [libesmtp] Not correctly linked against openssl 1.1] << in openssl 
1.1, SSL_library_init is a preprocessor macro, not an actual symbol; so 
libesmtp's ./configure erroneously thinks that libssl isn't available, >>

There is a technique for fixing this problem by modifying configure.ac at 
https://github.com/simsong/tcpflow/commit/985f0259a17dfce73f0e7d99990ba70f194cd515
but I don't see how to apply it to nut-2.7.4/configure.ac

Roger