[gecode] Bumped to 3.7.3 (Sync with HEC gecode version)
[nginx] CHEF-4227: Bump to 1.2.9 (fixes CVE-2013-2070)

Although CHEF-4227 requested a bump to Nginx 1.4.1, we've found that
Nginx 1.2.9 also fixes CVE-2013-2070. We want to keep the version of
Nginx in sync with Enterprise Chef's Openresty.