Ticket #3865: extfs: rpm: INSTALL is truncated in the viewer

Ticket #3865: extfs: rpm: INSTALL is truncated in the viewer

Before the rewrite e7ed071be7fda2df59191d103c47bf30a6b98ca8, the files
`INSTALL`, `UPGRADE`, and `REBUILD` were just text files with fixed
length of 39 characters. After the rewrite, the corresponding `rpm`
commands (of variable length) have been added.

If one of these files is being opened with the internal viewer, only the
first 39 characters (hardcoded in `mcrpmfs_list()`) are shown, e.g.
`INSTALL` (before the previous commit):

	# Run this script to install this RPM p

The word 'script' was added inconsistently (compare with `UPGRADE` and
`REBUILD`) and can be removed. The `rpm` commands can be also removed:
they may fail to work if there is a whitespace in the path, so they
cannot always be simply copy&pasted; it's is still possible to "run" the
script files with Enter.

Signed-off-by: Anatoly Borodin <anatoly.borodin@gmail.com>
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>