* .cvsignore: Don't ignore *.orig or *.rej.  They're not build products.
Don't ignore the entire m4 directory.
* Makefile.maint (sync-vcs-ignore-files): Correct quoting.
Use sed rather than a for loop.
Search only version-controled files (for reproducibility)
* gnulib/lib/netinet/.cvsignore: Append missing newline-at-EOF,
so that the use of sed doesn't mistakenly concatenate lines.
* gnulib/lib/sys/.cvsignore: Likewise.
* m4/.cvsignore: Ignore acinclude.m4 and aclocal.m4, not *.m4.
* .hgignore: Regenerate.
* all .gitignore files: Regenerate.