Let phex and phex_nz handle sizeof_l==1

Currently, neither phex nor phex_nz handle sizeof_l==1 -- they let
this case fall through to the default case.  However, a subsequent
patch in this series needs this case to work correctly.

I looked at all calls to these functions that pass a 1 for the
sizeof_l parameter.  The only such case seems to be correct with this
change.