DOC: spoe: Add a note about fragmentation support in HAProxy

Add a note in SPOE.txt to make it clear that HAPRoxy does not support the
fragmentation. It can send fragmented frames if an agent supports it but it
cannot receives and handles fragmented frames.

This patch should fix the issue #659. It may be backported as far as 1.8.

(cherry picked from commit 9536ad707f390c8026777ec8e074a5edaa2f7c7a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 71ebab63e0d8062b8795ac616d99730bc16f89d3)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 0f7a3a1d84d7df08c7cc2d2b2a7c95eefa0d9909)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 352aa05c45e8fdad4cd7ddc0d8d9663fc077bd2e)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/doc/SPOE.txt b/doc/SPOE.txt
index 3661602..4a2e3c1 100644
--- a/doc/SPOE.txt
+++ b/doc/SPOE.txt
@@ -762,6 +762,10 @@
 
 Unsupported or unknown capabilities are silently ignored, when possible.
 
+NOTE: HAProxy does not support the fragmentation for now. This means it is not
+      able to handle fragmented frames. However, if an agent announces the
+      fragmentation support, HAProxy may choose to send fragemented frames.
+
 3.2.2. Frame types overview
 ----------------------------