MFH: r469927

Update devel/libgit2 to 0.27.0 required for gitlab 10.7.x
Updated patches to match new file locations.

Reviewed by: swills (mentor), wg (maintainer)
Approved by: swills (mentor), wg (maintainer)
Differential Revision: https://reviews.freebsd.org/D15320

Approved by: ports-secteam (eadler)