Documentation note for Win32 glue between BIO layer and compiler run-time.

doc/crypto/OPENSSL_Applink.pod

@@ -0,0 +1,21 @@
+=pod
+
+=head1 NAME
+
+OPENSSL_Applink
+
+=head1 SYNOPSIS
+
+ __declspec(dllexport) void **OPENSSL_Applink();
+
+=head1 DESCRIPTION
+
+OPENSSL_Applink is application-side interface which provides a glue
+between OpenSSL BIO layer and Win32 compiler run-time environment.
+Even though it appears at application side, it's essentially OpenSSL
+private interface. For this reason application developers are not
+expected to implement it, but to compile provided module with
+compiler of their choice and link it into the target application.
+The referred module is available as <openssl>/ms/applink.c.
+
+=cut