doc: Mention Windows XP end of support in release notes

Closes #7681.

Author: laanwj

doc/release-notes.md

@@ -16,6 +16,28 @@ To receive security and update notifications, please subscribe to:
 
   <https://bitcoincore.org/en/list/announcements/join/>
 
+Compatibility
+==============
+
+Microsoft ended support for Windows XP on [April 8th, 2014](https://www.microsoft.com/en-us/WindowsForBusiness/end-of-xp-support),
+an OS initially released in 2001. This means that not even critical security
+updates will be released anymore. Without security updates, using a bitcoin
+wallet on a XP machine is irresponsible at least.
+
+In addition to that, with 0.12.x there have been varied reports of Bitcoin Core
+randomly crashing on Windows XP. It is [not clear](https://github.com/bitcoin/bitcoin/issues/7681#issuecomment-217439891)
+what the source of these crashes is, but it is likely that upstream
+libraries such as Qt are no longer being tested on XP.
+
+We do not have time nor resources to provide support for an OS that is
+end-of-life. From 0.13.0 on, Windows XP is no longer supported. Users are
+suggested to upgrade to a newer verion of Windows, or install an alternative OS
+that is supported.
+
+No attempt is made to prevent installing or running the software on Windows XP,
+you can still do so at your own risk, but do not expect it to work: do not
+report issues about Windows XP to the issue tracker.
+
 Notable changes
 ===============