Fix another bug reported by Andrey ``Bass'' Shcheglov.

* lib/framework.exp (xml_tag): Escape all of the non-printable control
  characters (ASCII codes 1 to 31 inclusive).

ChangeLog

@@ -1,3 +1,8 @@
+2017-08-19  Ben Elliston  <bje@gnu.org>
+
+	* lib/framework.exp (xml_tag): Escape all of the non-printable
+	control characters (ASCII codes 1 to 31 inclusive).
+
 2017-08-18  Tom Tromey  <tom@tromey.com>
 
 	* runtest.exp: Fix --directory matching.

lib/framework.exp

@@ -366,6 +366,12 @@ proc log_and_exit {} {
 # Emit an XML tag, but escape XML special characters in the body.
 proc xml_tag { tag body } {
     set escapes { < &lt; > &gt; & &amp; \" &quot; ' &apos; }
+    for {set i 1} {$i < 32} {incr i} {
+	# Append non-printable character
+	lappend escapes [format %c $i]
+	# .. and then the corresponding XML escape
+	lappend escapes &#[format %x $i]\;
+    }
     return <$tag>[string map $escapes $body]</$tag>
 }