Drop .cvsignore and redundant .gitignore files.

Drop .cvsignore and redundant .gitignore files.

* .cvsignore: Delete.  We are moving further away from CVS.
* build-aux/.cvsignore: Likewise.
* doc/.cvsignore: Likewise.
* examples/.cvsignore: Likewise.
* ltdl/.cvsignore: Likewise.
* m4/.cvsignore: Likewise.
* modules/.cvsignore: Likewise.
* po/.cvsignore: Likewise.
* src/.cvsignore: Likewise.
* tests/.cvsignore: Likewise.
* .gitignore: Consolidate from other files.
* build-aux/.gitignore: Delete, now that it is consolidated.
* doc/.gitignore: Likewise.
* examples/.gitignore: Likewise.
* ltdl/.gitignore: Likewise.
* m4/.gitignore: Likewise.
* modules/.gitignore: Likewise.
* po/.gitignore: Likewise.
* src/.gitignore: Likewise.
* tests/.gitignore: Likewise.
* bootstrap: Simplify accordingly.  Sync gnulib tree prior to
libtoolize, to avoid libtool overwriting config.guess.

Signed-off-by: Eric Blake <ebb9@byu.net>
(cherry picked from commit 76b384f1d84225d0412d58999d2becc8936dd645)