fixed the letcharcode example

[[Split portion of a mixed commit.]]

manual/luatex-enhancements.tex

@@ -736,7 +736,7 @@ This primitive is still experimental but can be used to assign a meaning to an a
 character, as in:
 
 \starttyping
-\def\foo{bar} \letcharcode123\foo
+\def\foo{bar} \letcharcode123=\foo
 \stoptyping
 
 This can be a bit nicer that using the uppercase tricks (using the property of