[ng] dejagnu: include verbatim

* lib/am/dejagnu.am: Rename ...
* lib/am/dejagnu.mk: ... like this, and rewrite partially to make it
readable verbatim.
* Makefile.am (dist_am_DATA): Adjust.
* automake.in (handle_tests): When DejaGNU support is needed, include
'dejagnu.mk' verbatim in the output Makefile.

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

diff --git a/lib/am/dejagnu.am b/lib/am/dejagnu.mk
similarity index 100%
rename from lib/am/dejagnu.am
rename to lib/am/dejagnu.mk