Fix convert_to_absolute_path

[minhqdao]

Hotfixing a bug in convert_to_absolute_path.

This doesn't work:

  character(len=*), intent(inout) :: path
  ...
  path = absolute_path

Therefore using a deferred type parameter.

  character(len=:), allocatable, intent(inout) :: path
  ...
  path = absolute_path

[henilp105]

Thanks @minhqdao , looks good to me.

[awvwgk]

Thanks for sharing.