Tweak, extend and improve tests `cond[a-z]*.test'.

Tweak, extend and improve tests `cond[a-z]*.test'.

* tests/condd.test: Add trailing `:' command.  Typofix in
comment.
* tests/condhook.test: Make sure target `install-data-hook' is
not called by `make install', but that data files are installed.
Use proper m4 quoting in configure.in. Add trailing `:' command.
* tests/condhook2.test: New test, sister test of condhook, with
inverted semantic.
* tests/condinc2.test: Use proper m4 quoting in configure.in.
Prefer trailing `:' command over trailing `Exit 0'.
* tests/condman2.test: Enable errexit shell flag, and related
changes.  Add trailing `:' command.
* tests/condman.test: Likewise.  Also, do not create useless
dummy manpages, and use proper m4 quoting in configure.in.
* tests/condman3.test: New test, similar to condman.test, but
it also runs ./configure and "make install", and check the
installed files.
* tests/Makefile.am (TESTS): Updated.