gzip: remove --__bindir

gzip: remove --__bindir

* NEWS: Document this.
* gzexe.in, gunzip.in, zcat.in, zcmp.in, zdiff.in, zegrep.in:
* zfgrep.in, zforce.in, zgrep.in, zless.in, zmore.in, znew.in:
Remove support for undocumented --__bindir option.  Callers can
set PATH instead; that's less error-prone.  This fixes some
'make check' failures on my Solaris 11 box, which occurred
because the test scripts were mistakenly testing the installed
gzip rather than the gzip in the working directory.
* Makefile.am (.in): Don't replace bindir.
(check-local): Set PATH instead of using --__bindir.
* tests/help-version (gunzip_setuphelp, gzexe_setuphelp)
(zcat_setuphelp, zcmp_setuphelp, zdiff_setuphelp)
(zegrep_setuphelp, zfgrep_setuphelp, zforce_setuphelp)
(zgrep_setuphelp, zless_setuphelp, zmore_setuphelp)
(znew_setuphelp): Remove.  All uses removed.
(lbracket_setup): Default args to empty.