git: update for git 2.0

prefixcmp() and suffixcmp() have been remove, functionality is now
provided by starts_with() and ends_with(). Retrurn values have been
changed, so instead of just renaming we have to fix logic.
Everything else looks just fine.
diff --git a/ui-clone.c b/ui-clone.c
index d25553b..a4ffd6e 100644
--- a/ui-clone.c
+++ b/ui-clone.c
@@ -63,7 +63,7 @@
 	}
 	ctx.page.mimetype = "application/octet-stream";
 	ctx.page.filename = path;
-	if (prefixcmp(ctx.repo->path, path))
+	if (!starts_with(ctx.repo->path, path))
 		ctx.page.filename += strlen(ctx.repo->path) + 1;
 	cgit_print_http_headers();
 	html_include(path);