[gmime] Updated PORTING to document changes from 2.6 to 3.0

[Jeffrey Stedfast <fejj src gnome org>]

commit 704024ecc6251822ad49ea037021408b09582a7b
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Sat Feb 4 22:12:45 2017 -0500

    Updated PORTING to document changes from 2.6 to 3.0

 PORTING |   39 +++++++++++++++++++++++++++++++++++++++
 1 files changed, 39 insertions(+), 0 deletions(-)
---
diff --git a/PORTING b/PORTING
index 102dddb..a413bc5 100644
--- a/PORTING
+++ b/PORTING
@@ -9,6 +9,45 @@ will attempt to list the main things to watch out for when migrating
 to the new release from the prior version.
 
 
+Porting from GMime 2.6 to GMime 3.0
+-----------------------------------
+
+- g_mime_message_get_sender() no longer returns the value of the From header,
+  it now returns an InternetAddressList* containing the parsed address(es)
+  from the Sender header. For the From addresses, use g_mime_message_get_from().
+
+- g_mime_message_get_reply_to() no longer returns a const char*, instead it
+  returns an InternetAddressList* for easier use.
+
+- g_mime_message_set_sender() and g_mime_message_set_reply_to() have been
+  removed. You will either need to use the appropriate getter method and
+  then internet_address_add_address() to add a new InternetAddressMailbox
+  or, alternatively, you can use g_mime_message_add_mailbox().
+
+- GMimeRecipientType has been replaced by GMimeAddressType because it now
+  contains non-recipient-based enum values (SENDER, FROM, and REPLY_TO).
+
+- g_mime_message_get_recipients() has been replaced by g_mime_message_get_addresses()
+  which allows you to access the address lists of any address header.
+
+- g_mime_message_add_recipient() has been renamed to g_mime_message_add_mailbox()
+  due to the fact that it can now be used to add mailbox addresses to the
+  Sender, From, and Reply-To headers as well.
+
+- GMimeObject's prepend_header(), append_header(), and set_header() virtual
+  methods now all take a const char *raw_value and gint64 offset arguments.
+  The raw_value is the raw header value cloned exactly as the parser found
+  it in the stream (meaning it retains the original folding). The 'value'
+  argument remains as it has always been, an unfolded (but still encoded)
+  header value.
+
+- GMimeHeaderIter has been dropped in favour of a more direct way of
+  iterating over a GMimeHeaderList using int indexes.
+
+- g_mime_stream_write_to_stream(), g_mime_stream_writev(), and g_mime_stream_printf()
+  now return a gint64.
+
+
 Porting from GMime 2.4 to GMime 2.6
 -----------------------------------