[3064] Revert "[2893]Use P_TEXT_SUPPORT_LEGACY and better messages"

This reverts commit 7f7f94c489e67c9baf7886dd77bc5d58015c04ed.
[3064] Revert "[2893]Only open (read-only) document with system viewer if preferences.P_TEXT_MULTIPLE is set"

This reverts commit 16d4f3b5a056fa3184d207db8af381e25385399c.