Default list of directories to search for Info documentation files.
They are searched in the order they are given in the list.
Therefore, the directory of Info files that come with Emacs
normally should come last (so that local files override standard ones),
unless Emacs is installed into a non-standard directory. In the latter
case, the directory of Info files that come with Emacs should be
first in this list.
Once Info is started, the list of directories to search
comes from the variable `Info-directory-list'.
This variable `Info-default-directory-list' is used as the default
for initializing `Info-directory-list' when Info is started, unless
the environment variable INFOPATH is set.
Although this is a customizable variable, that is mainly for technical
reasons. Normally, you should either set INFOPATH or customize
`Info-additional-directory-list', rather than changing this variable.