maint: make our use of gnulib's init.sh conform

maint: make our use of gnulib's init.sh conform

* tests/help-version: Make use of init.sh conform.
* tests/helin-segv: Likewise.
* tests/help-version: Likewise.
* tests/hufts: Likewise.
* tests/memcpy-abuse: Likewise.
* tests/mixed: Likewise.
* tests/null-suffix-clobber: Likewise.
* tests/stdin: Likewise.
* tests/trailing-nul: Likewise.
* tests/zdiff: Likewise.
* tests/zgrep-f: Likewise.
* tests/zgrep-signal: Likewise.
* tests/znew-k: Likewise.