/usr/share/highlight/langDefs/txt.lang is in highlight-common 3.9-1+deb7u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 | Description="Plain text"
Keywords={
}
Comments={
}
-- disable highlighting of numbers
Digits = Identifiers
EnableIndentation=true
|