For all possibly-relative subdirs, use $(am__cd).

For all possibly-relative subdirs, use $(am__cd).

Up to now, $(am__cd) was only used within backquotes, to avoid
extraneous output.  This patch also uses it for every `cd' to a
relative subdir, to prevent CDPATH from entering an unwanted
directory.
* Makefile.am (maintainer-check): Fix current check for
$(am__cd) within backquotes a bit.  Add new check for `cd' to a
relative subdir.
* automake.in (handle_tags, handle_configure):  Adjust rules.
* lib/am/ansi2knr.am: Likewise.
* lib/am/configure.am: Likewise.
* lib/am/distdir.am: Likewise.
* lib/am/remake-hdr.am: Likewise.
* lib/am/subdirs.am: Likewise.
* lib/am/tags.am: Likewise.
* lib/am/texibuild.am: Likewise.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>