[DRE-maint] Bug#900297: ruby-ethon: switch dependency to libcurl4

[Emilio Pozuelo Monfort]

Package: ruby-ethon
Version: 0.9.0-1
Severity: serious
Tags: buster sid

Hi,

curl has bumped the SONAME to libcurl4 for the openssl 1.1 ABI.
Please update the dependency to libcurl4.

Note that Ubuntu has already done the switch and they had some
remarks wrt the ABI:

ruby-ethon (0.9.0-1ubuntu1) bionic; urgency=medium

  * Bump dependency from libcurl3 to libcurl4 for the openssl1.1 transition.
    Note that this changes the ABI with respect to SSL_CTX objects;
    consumers of ruby-ethon must now switch to using OpenSSL 1.1 objects
    instead of OpenSSL 1.0 if they use curl_easy_setopt(SSL_CTX_FUNCTION).

 -- Steve Langasek <steve.langasek at ubuntu.com>  Thu, 01 Mar 2018 21:49:45 -0800

Cheers,
Emilio