1) ops

   stat (out PMC, in STR, in INT)
   stat (out PMC, in PMC, in INT)

Return a new array-like[1] PMC $1 with file stats from file (PIO or
string) $2,
or PerlUndef, if file doesn't exist, $3 are flags:

   .PARROT_STAT_NO_FOLLOW_LINK

The array(-like)  has keyed access with these keys

   .PARROT_STAT_FILE_SIZE
   .PARROT_STAT_FILE_SIZE_LO
   .PARROT_STAT_FILE_SIZE_HI

   .PARROT_STAT_MODE a bitmask with these bits:
      .PARROT_STAT_MODE_ISDIR
      .PARROT_STAT_MODE_ISFILE
      [ more platform-unspecific bits ]

   .PARROT_STAT_PERM a bitmask with these bits
      .PARROT_STAT_PERM_IS_READABLE
      .PARROT_STAT_PERM_IS_WRITABLE
      .PARROT_STAT_PERM_IS_EXECUTABLE

   .PARROT_STAT_MTIME modified time

   .PARROT_STAT_OS_TYPE a constant defining the os-specific
      part that follows
        .PARROT_STAT_stat
        .PARROT_STAT_stat64
        ...

   .PARROT_STAT_OS_SPECIFIC
       A (Un)?ManagedStruct PMC with OS-specific data like a
        struct stat64

2) Interface

    PMC* Parrot_stat_s(Interp*, STRING* file, INTVAL flags);
    PMC* Parrot_stat_p(Interp*, PMC*    pio,  INTVAL flags);

3) Interface to platforms

    INTVAL Parrot_stat_os_s(Interp*, Parrot_stat*, STRING* file, INTVAL
flags);
    INTVAL Parrot_stat_os_p(Interp*, Parrot_stat*, PMC*    pio,  INTVAL
flags);

    typedef struct _parrot_stat {
       size64_t size;
       UINTVAL mode;
       UINTVAL perm;
       FLOATVAL mtime;  // in Parrot units
       UINTVAL os_stat_type;
       union {
         struct stat;
        struct stat64;
        ...
      } u;
    } Parrot_stat;

4) Notes
The information in the first few fields should not be platform
specific. If platforms have more in common then above bits, the
structure should be expanded.

[1] it needs just these vtables implemeted: I0 = P0[i], N0 = P0[i],
i.e. get_{integer,number}_keyed_int

Comments, improvements, and implementations thereafter welcome
leo