Specialize GetMemoryOfBuiltinAsString for <char> to customize the display of
non-printable characters. All characters will now be printed as 'X', where X
is the character value. If a non-printable character value matches \t, \f, \v,
\n, or \r, then it will be printed using the escape sequence, otherwise it will
be printed using the integer value of the character, e.g. \0.