Merge branch 'msvc' into maint

Merge branch 'msvc' into maint

This merge remedies the confusing situation that some changes
destined for both the master branch and the release branch (a.k.a.
branch-1.11) currently needs to be made on the non-obvious msvc
branch and not on the more natural maint branch.  This has caused
a seemingly endless string of less than optimal commits.

The reason for the confusion stems from the fact that the changes made
on the msvc branch became too radical and was considered only suitable
for the master branch, and was thus written in a form suitable for
master and then merged there.  Later, the msvc branch was merged
directly into branch-1.11, in order to rush the new features to the
market and to keep the released scripts (lib/ar-lib, lib/compile and
lib/depcomp) consistent with those on the master branch.  However,
some changes had to be made to the features added by the msvc branch
in order for them to fit the requirements of branch-1.11, notably that
the warnings issued in the extra-portability class cannot be enabled
by -Wall in the 1.11.x maintenance releases.

In retrospect, it would have been better to not merge msvc directly
into branch-1.11, but instead do it via the maint branch (followed up
with a dummy merge from maint into master) the moment it was decided
that the msvc changes should make it into branch-1.11.

All in all, this merge is going to affect neither the master branch
nor branch-1.11, since it is followed up with dummy merges masking all
changes.  The merge is made to maintain the sanity of the poor
developers, who wishes to once again have a working maint branch.

Discussion about merging the msvc branch into branch-1.11:
http://lists.gnu.org/archive/html/automake/2011-10/msg00030.html

Discussion about why this merge hasn't happened before:
http://lists.gnu.org/archive/html/automake/2011-12/msg00051.html

Extra edits below.

* lib/Automake/ChannelDefs.pm: Use the version from branch-1.11.
* tests/ar-lib3.test: Likewise.
* tests/ar-lib4.test: Likewise.
* tests/extra-portability.test: Likewise.
* tests/extra-portability2.test: Likewise.
* tests/extradep.test: Likewise.
* tests/extradep2.test: Likewise.
* tests/list-of-tests.mk: Likewise.
* HACKING: Backport the version from branch-1.11 while at it (as the
change on branch-1.11 is also present on master via an unrelated
commit), even though this change has nothing to do with the changes
on the msvc branch.