Add libssl to bindep

Source builds using cryptography need libssl-dev (and assorted other
platform package names) to compile. Adding package declaration for
dpkg, rpm, and suse.

Change-Id: I9238cc977529c46470479656e449ea6cef4ae5fb
Closes-bug: #1696712

bindep.txt

@@ -10,3 +10,6 @@ libxml2-devel [platform:rpm]
 libxml2-dev [platform:dpkg]
 libxslt-devel [platform:rpm]
 libxslt1-dev [platform:dpkg]
+libssl-dev [platform:dpkg]
+openssl-devel [platform:rpm !platform:suse]
+libopenssl-devel [platform:suse !platform:rpm]