Update libgit2 to 0.26
Update libgit2 to 0.26

Really, sometimes after 0.26, because of a test .gitmodules which would make Travis fail.

libgit2/objective-git,blackpixel/objective-git,libgit2/objective-git,alehed/objective-git,phatblat/objective-git,libgit2/objective-git,libgit2/objective-git,phatblat/objective-git,tiennou/objective-git,tiennou/objective-git,phatblat/objective-git,tiennou/objective-git,dleehr/objective-git,alehed/objective-git,alehed/objective-git,dleehr/objective-git,dleehr/objective-git,dleehr/objective-git,blackpixel/objective-git,blackpixel/objective-git,blackpixel/objective-git