cmd/cgo,doc/go1.12.html: document breaking EGLDisplay change

Change-Id: I3c8ba5fdb05b6b1324648622656cc10071c70a34
Reviewed-on: https://go-review.googlesource.com/c/154997Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.12.html

@@ -135,6 +135,16 @@ Do not send CLs removing the interior tags from such phrases.
   Go 1.12 is the last release that will support binary-only packages.
 </p>
 
+<h3 id="cgo">Cgo</h3>
+
+<p>
+	Go 1.12 will translate the C type <code>EGLDisplay</code> to the Go type <code>uintptr</code>.
+	This change is similar to how Go 1.10 and newer treats Darwin's CoreFoundation
+	and Java's JNI types. See the
+	<a href="https://golang.org/cmd/cgo/#hdr-Special_cases">cgo documentation</a>
+	for more information.
+</p>
+
 <h3 id="modules">Modules</h3>
 
 <p><!-- CL 148517 -->

src/cmd/cgo/doc.go

@@ -413,6 +413,8 @@ type in Go are instead represented by a uintptr. Those include:
 	jobjectArray
 	jweak
 
+3. The EGLDisplay type from the EGL API.
+
 These types are uintptr on the Go side because they would otherwise
 confuse the Go garbage collector; they are sometimes not really
 pointers but data structures encoded in a pointer type. All operations
@@ -427,6 +429,11 @@ from Go 1.9 and earlier, use the cftype or jni rewrites in the Go fix tool:
 
 It will replace nil with 0 in the appropriate places.
 
+The EGLDisplay case were introduced in Go 1.12. Use the egl rewrite
+to auto-update code from Go 1.11 and earlier:
+
+	go tool fix -r egl <pkg>
+
 Using cgo directly
 
 Usage: