Improve tests on generated portions of configure help screen.

Improve tests on generated portions of configure help screen.

* tests/help-depend.test: Grepping of configure help screen
relaxed to cater for possible line wrapping, and tightened in
other respects.
* tests/help-depend2.test: Likewise.
* tests/help-dmalloc.test: Likewise.
* tests/help-lispdir.test: Likewise.
* tests/help-maintainer.test: Likewise.
* tests/help-multilib.test: Likewise.
* tests/help-silent.test: Likewise.
* tests/help-upc.test: Likewise.
* tests/help-init.test: Grepping of configure help screen
tightened.