texi: no longer support split info files

texi: no longer support split info files

See automake bug#13351 and bug#12320.

Automake-generated recipes have for a long time supported "split"
info files:

  http://www.gnu.org/software/texinfo/manual/texinfo/texinfo.html#Tag-and-Split-Files

When I asked the rationale for this feature:

  http://lists.gnu.org/archive/html/texinfo-devel/2012-08/msg00015.html

Karl Berry confirmed that the reason for its existence was indeed
"efficiency, especially memory size":

  http://lists.gnu.org/archive/html/texinfo-devel/2012-08/msg00024.html

He also added that "The Elisp manual is one of the largest ones around.
Looks like it would be maybe 3.5mb as one file."  Not in any way big by
modern standards.

OTOH, it appears that the use of split info files (at least in the way
they have been handled by Automake-generated rules for a long time) can
cause real problems in some (admittedly quite corner-case) situations:

  http://thread.gmane.org/gmane.comp.parsers.bison.bugs/3963
  http://debbugs.gnu.org/cgi/bugreport.cgi?bug=12320

So we now follow suit with Automake-NG (see commit v1.12.2-901-gdd603e2,
<http://lists.gnu.org/archive/html/automake-ng/2012-08/msg00147.html>)
and have Automake-generated makefiles pass the '--no-split' option
unconditionally to makeinfo invocations.

This allow some nice simplifications in our Texinfo recipes, and offer
an automatic fix for bug#12320.

Another *very* good aspect of such a change is that it should be 100%
transparent to the Automake users.

* lib/am/texinfos.am: Simplify moderately.
* lib/am/texibuild.am: Simplify greatly the recipe for the creation
of info files.
* t/txinfo-makeinfo-error-no-clobber.sh: Adjust.
* t/txinfo-no-split.sh: New test.
* t/list-of-tests.mk: Add it.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>