missing padding by leading zeroes, where applicable

[nbehrnd]

The submission of the following snippet of code

program test
   implicit none(external)
   integer :: a, square

   do a = 1, 5
      square = a ** 2
      write (*, "(2(I3.3, 1x))") a, square
   end do
 
end program test

to LFORTRAN (commit b5e05bd3a) results in frame STDOUT the output of

1 1
2 4
3 9
4 16
5 25

Compilation time: 95 ms
Execution time: 1 ms

This contrasts with my expectation to 1) yield columns of constant width aligned to the right hand side, and 2) a padding with leading zeroes (001, 016, etc) where applicable.

[certik]

This is what I get locally using LLVM:

$ lfortran a.f90
001 001
002 004
003 009
004 016
005 025

So I think it's implemented correctly at least with LLVM, but we need to update our direct WASM backend.