The package provides macros \DeclareRobustActChar and
\ReDeclareRobActChar. One uses \DeclareRobustActChar in the
same way one would use \DeclareRobustCommand; the macro
\protects the active character when it appears in a moving
argument. \ReDeclareRobActChar redefines an active character
previously defined with \DeclareRobustActChar, in the same way
that \renewcommand works for ordinary commands.
