libgit2: fix gcc2 build.

This is needed for the work on the Git Tracker add-on for GSoC.

dev-libs/libgit2/patches/libgit2-0.26.3.patchset

@@ -0,0 +1,71 @@
+From 4036019821be1f94bed724e2ebdb2a3b6ff41670 Mon Sep 17 00:00:00 2001
+From: Adrien Destugues <pulkomandy@pulkomandy.tk>
+Date: Thu, 10 May 2018 10:21:34 +0200
+Subject: Reorder some includes to avoid conflicts between zlib and openssl
+
+zlib #defines free_func, but ssl headers use free_func in a parameter
+name in some places. This ends up confusing gcc2. Make sure the ssl
+headers are included before the define is set, so we can build libgit
+with gcc2.
+
+diff --git a/src/fetch.c b/src/fetch.c
+index f408a51..9bf58fc 100644
+--- a/src/fetch.c
++++ b/src/fetch.c
+@@ -5,6 +5,8 @@
+  * a Linking Exception. For full terms see the included COPYING file.
+  */
+ 
++#include "netops.h"
++
+ #include "git2/oid.h"
+ #include "git2/refs.h"
+ #include "git2/revwalk.h"
+@@ -15,7 +17,6 @@
+ #include "refspec.h"
+ #include "pack.h"
+ #include "fetch.h"
+-#include "netops.h"
+ #include "repository.h"
+ #include "refs.h"
+ 
+diff --git a/src/pack-objects.h b/src/pack-objects.h
+index e1e0ee3..399a035 100644
+--- a/src/pack-objects.h
++++ b/src/pack-objects.h
+@@ -8,12 +8,13 @@
+ #ifndef INCLUDE_pack_objects_h__
+ #define INCLUDE_pack_objects_h__
+ 
++#include "netops.h"
++
+ #include "common.h"
+ 
+ #include "buffer.h"
+ #include "hash.h"
+ #include "oidmap.h"
+-#include "netops.h"
+ #include "zstream.h"
+ #include "pool.h"
+ #include "indexer.h"
+diff --git a/src/push.c b/src/push.c
+index 433cc06..a112fc1 100644
+--- a/src/push.c
++++ b/src/push.c
+@@ -5,11 +5,12 @@
+  * a Linking Exception. For full terms see the included COPYING file.
+  */
+ 
++#include "pack-objects.h"
++
+ #include "git2.h"
+ 
+ #include "common.h"
+ #include "pack.h"
+-#include "pack-objects.h"
+ #include "remote.h"
+ #include "vector.h"
+ #include "push.h"
+-- 
+2.16.2
+