explain why the ABI depends on the SSL libs

docs/DISTRO-DILEMMA

-Date: September 1, 2005
-Author: Daniel Stenberg <daniel@haxx.se>
-URL: http://curl.haxx.se/legal/distro-dilemma.html
+  Date: September 2, 2005
+  Author: Daniel Stenberg <daniel@haxx.se>
+  URL: http://curl.haxx.se/legal/distro-dilemma.html
 
 Condition
 
@@ -116,6 +116,16 @@ Project cURL Angle of this Problem
  affects users - GPL application authors only - of our lib as it comes
  included and delivered on some distros.
 
+ libcurl has different ABI when built with different SSL/TLS libraries due to
+ two reasons:
+
+ 1. No one has worked on fixing this. The mutex/lock callbacks should be set
+    with a generic libcurl function that should use the proper underlying
+    functions.
+
+ 2. The CURLOPT_SSL_CTX_FUNCTION option is not possible to "emulate" on GnuTLS
+    but simply requires OpenSSL.
+
 Distro Angle of this Problem
 
  A distro can provide separate libcurls built with different SSL/TLS libraries