Use copy_to_all_selections if possible on --copy.

[shlomif]

This allows ctrl+v on X windows.

---

I hereby disclaim any implicit or explicit ownership of my changes in this
changeset, and put them under a multiple licence consisting of your choice of
one of more of:

• The CC0 / Public Domain - https://creativecommons.org/choose/zero/ .

• The MIT / Expat license - https://en.wikipedia.org/wiki/MIT_License

• The default licence of your project

• The https://en.wikipedia.org/wiki/GNU_Lesser_General_Public_License - version
  2.1 or higher

• The https://en.wikipedia.org/wiki/GNU_General_Public_License - version 2 or
  higher

• Any licence in the 2018-Aug-27 popular licenses list of
  https://opensource.org/licenses

• The https://en.wikipedia.org/wiki/Apache_License version 2.0 or later

• The https://en.wikipedia.org/wiki/Artistic_License version 2.0 or later

• The https://en.wikipedia.org/wiki/ISC_license

• The https://opensource.org/licenses/BSD-2-Clause

Crediting me will be nice, but not mandatory, and you can change the licence
of the project without needing my permission.

[karenetheridge]

Instead of checking $@ (which might not be set properly, or defined-and-false), it would be preferrable to check the result, like so:

eval { <first call>; 1 } or <second call>;

[shlomif]

@karenetheridge : hopefully fixed now.

[shlomif]

@karenetheridge : thanks!