MFH: r477236

lang/chicken: Update to 4.13.0

• Respect LDFLAGS
• Take maintainership

Changes: https://code.call-cc.org/releases/4.13.0/NEWS
PR: 230535
Approved by: maintainer
Security: 5a771686-9e33-11e8-8b2d-9cf7a8059466

Approved by: ports-secteam (miwi)