vcl: use enum for complex text layout constants

Since these constants are bitfield flags, we define some methods to make
working with them reasonably type safe.

Move the definitions to outdevstate.hxx, since we need the values there,
and that appears to be the "root most" header file.

Also dump TEXT_LAYOUT_BIDI_LTR constant, since it means the same thing
as TEXT_LAYOUT_DEFAULT (ie. 0), and leaving it in causes people to write
weird code thinking that it's a real flag.

Change-Id: Iddab86cd6c78181ceb8caa48e77e1f5a8e526343
Reviewed-on: https://gerrit.libreoffice.org/10676
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>