OpenSSL: Add build option to select default ciphers

OpenSSL: Add build option to select default ciphers

Add a build option to select different default ciphers for OpenSSL
instead of the hardcoded default "DEFAULT:!EXP:!LOW".

This new option is useful on distributions where the security level
should be consistent for all applications, as in Fedora [1]. In such
cases the new configuration option would be set to "" or
"PROFILE=SYSTEM" to select the global crypto policy by default.

[1] https://fedoraproject.org/wiki/Changes/CryptoPolicy

Signed-off-by: Beniamino Galvani <bgalvani@redhat.com>