tests: more significant names for some tests

tests: more significant names for some tests

* t/extra5.sh: Rename ....
* t/extra-dist-vpath-dir.sh: ... like this.
* t/extra6.sh: Rename ....
* t/extra-dist-dirs-and-subdirs.sh: ... like this.
* t/extra7.sh: Rename ....
* t/extra-dist-vpath-dir-merge.sh: ... like this.
* t/extra8.sh: Rename ....
* t/extra-programs-misc.sh: ... like this.
* t/extra9.sh: Rename ....
* t/extra-programs-and-libs.sh: ... like this.
* t/extra10.sh: Rename ....
* t/extra-dist-wildcards.sh: ... like this.
* t/extra11.sh: Rename ....
* t/extra-dist-wildcards-gnu.sh: ... like this.
* t/extra12.sh: Rename ....
* t/extra-dist-wildcards-vpath.sh: ... like this.
* t/extradep.sh: Rename ....
* t/extra-deps.sh: ... like this, and adjust heading comments.
* t/extradep2.sh: Rename ....
* t/extra-deps-lt.sh: ... like this, and adjust heading comments.
* t/list-of-tests.mk: Adjust.

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