[ng] cleanup: remove a workaround only needed by Solaris make

[ng] cleanup: remove a workaround only needed by Solaris make

The workaround was introduced in commit 'v1.11-257-g20fb9ce' of
2010-05-14, "Work around a bug in file-inclusion mechanism of
Solaris make".

* automake.in (handle_single_transform): When calculating the name
of the dependency file, don't bother collapsing multiple slash
characters into a single one.
* t/subobj11a.sh: Adjust comments.  Prefer calling "fatal_ MSG" over
"echo MSG >&2; Exit 1" for hard errors.
* t/subobj11c.sh: Remove as obsolete.

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