soft require openssl

[michaelortmann]

Found by: Geo
Patch by: michaelortmann
Fixes: #1366

One-line summary:
Change compile process to fail if openssl is not present, or --disable-tls is not explicitly stated.

Additional description (if needed):
Please run misc/runautotools when testing / merging this PR

Test cases demonstrating functionality (if applicable):
needs more testing

[vanosg]

I ran misc/autoruntools, but it still seems to compile with a clean ./configure:

<snip>
checking whether to enable TLS support... autodetect
checking for openssl/ssl.h... no
checking for openssl/x509v3.h... no
checking for X509_digest in -lcrypto... no
checking for SSL_accept in -lssl... no
checking for EVP_sha1... no
checking for EVP_md5... no
checking for OPENSSL_buf2hexstr... no
checking for hex_to_string... no
checking for OPENSSL_hexstr2buf... no
checking for string_to_hex... no
checking for OpenSSL... no (make sure you have version 0.9.8 or higher installed)
<snip>

SSL/TLS Support: no
Threaded DNS core: yes

If you experience any problems compiling Eggdrop, please read the
compile guide, found in doc/COMPILE-GUIDE.

Type 'make config' to configure the modules, or type 'make iconfig'
to interactively choose which modules to compile.

[vanosg]

Ok, fixed the issue with autoconf on my side. With no TLS libs:

checking for string_to_hex... no
configure: WARNING: Cannot find OpenSSL headers.
configure: WARNING: Please specify the path to the openssl include dir using --with-sslinc=path
configure: WARNING: Cannot find OpenSSL libraries.
configure: WARNING: Please specify the path to libssl and libcrypto using --with-ssllib=path
checking for OpenSSL... no
* We tried, but couldn't find TLS libraries. If installed, please specify their paths using the configure flags above
* While not recommended, you can continue without TLS protection by specifying the --disable-tls configure flag
configure: error: TLS Libraries not found

No TLS libs, and --disable-tls:

<no checks for OpenSSL>
Operating System: Linux 6.2.0-32-generic
IPv6 Support: yes
Tcl version: 8.6.10 (threaded)
SSL/TLS Support: no
Threaded DNS core: yes

TLS installed:

Operating System: Linux 6.2.0-32-generic
IPv6 Support: yes
Tcl version: 8.6.10 (threaded)
SSL/TLS Support: yes (OpenSSL 1.1.1f  31 Mar 2020)
Threaded DNS core: yes

TLS installed, --disable-tls used:

Operating System: Linux 6.2.0-32-generic
IPv6 Support: yes
Tcl version: 8.6.10 (threaded)
SSL/TLS Support: no
Threaded DNS core: yes