Add support for other standard length modifiers

[Snaipe]

The C99 spec defines the following additional modifiers:

hh     A following integer conversion corresponds to a signed char or 
       unsigned char argument, or a following n conversion corresponds
       to a pointer to a signed char argument.
h      A following integer conversion corresponds to a short int or unsigned
       short int argument, or a following n conversion corresponds to a
       pointer to a short int argument.
L      A following a, A, e, E, f, F, g, or G conversion corresponds to a
       long double argument.
j      A following integer conversion corresponds to an intmax_t or
       uintmax_t argument, or a following n conversion corresponds to a
       pointer to an intmax_t argument.
t      A following integer conversion corresponds to a ptrdiff_t argument,
       or a following n conversion corresponds to a pointer to a ptrdiff_t
       argument.

It would be good to support those for people that want a standard-compliant printf replacement.

h and hh should be relatively straightforward, as char and short decay to int in varargs; so they should just be accepted, but do nothing.