message: bindings/fortran: add test for adios2_variable_name
diff: type(adios2_variable), dimension(13) :: variables
  type(adios2_engine) :: bpWriter, bpReader
  character(len=15) :: inString
  + character(len=:), allocatable :: varName
  ! read handlers
  integer :: ndims
  if( variables(i)%valid .eqv. .false. ) stop 'Invalid adios2_define_variable'
  end do
  + ! Testing adios2_variable_name for just two cases
  + call adios2_variable_name(varName, variables(1), ierr)
  + if (varName /= 'var_I8') stop 'Invalid adios2_variable_name'
  +
  + call adios2_variable_name(varName, variables(2), ierr)
  + if (varName /= 'var_I16') stop 'Invalid adios2_variable_name'
  +
  + deallocate(varName)
  +
  ! Open myVector_f.bp in write mode, this launches an engine
  if( ioWrite%valid .eqv. .false. ) stop 'Invalid adios2_io'
  if( bpWriter%valid .eqv. .true. ) stop 'Invalid adios2_engine pre-open'
  