Fix Texinfo error.

ChangeLog

@@ -4,6 +4,7 @@
 	* doc/Makefile.am (protocol-a.texi): Use '@"a', not '@"a{}', when
 	substituting IAM.
 	* doc/Protocol-A.texi (IAM): Use '@"a', not '@"a{}'.
+	* doc/constructs.expected: @"a{} is no longer used.
 
 	"make check" / Python 1.5 compatibility fixes.
 	* doc/checkargs.py (lexer.__init__): Use string.split for Python