correct and tighten up .*ignore files

* .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.

.cvsignore

@@ -1,7 +1,5 @@
 *.a
 *.o
-*.orig
-*.rej
 *~
 .git
 ABOUT-NLS
@@ -27,7 +25,6 @@ libvirt.pc
 libvirt.spec
 ltconfig
 ltmain.sh
-m4
 mingw32-libvirt.spec
 mkinstalldirs
 results.log

.gitignore

@@ -1,7 +1,5 @@
 *.a
 *.o
-*.orig
-*.rej
 *~
 .git
 ABOUT-NLS
@@ -27,7 +25,6 @@ libvirt.pc
 libvirt.spec
 ltconfig
 ltmain.sh
-m4
 mingw32-libvirt.spec
 mkinstalldirs
 results.log