Bug#566008: say where to obtain the list of -names

[jidanni@jidanni.org]

Package: x11-utils
Version: 7.5+1
Severity: wishlist
File: /usr/share/man/man1/xwininfo.1.gz

in man xwininfo and man xprop, we see we can use -name.
However these man pages don't tell us how we can get a list of what the
current names are. Please add how.

(One would think that they are the same as the ones at the bottom of the
screen, in e.g., icewm, but in fact they are the ones seen with ALT+TAB.
Mostly the same, but not always.)

(Also, some of those names are quite long. The user should be allowed to
use unique abbreviations or even *xyz wildcards perhaps, if they uniquely
match one window name.)