Prefer mcel to mbuiter

Prefer the lighter-weight mcel implementation to the heavier-weight
mbuiter that GNU tar does not need.
* bootstrap.conf (avoided_gnulib_modules): Avoid mbuiter, mbuiterf.
* gnulib.modules: Add mcel-prefer.

bootstrap.conf

@@ -20,10 +20,12 @@
 source_base=gnu
 gnulib_name=libgnu
 
-# We don't need these modules, even though gnulib-tool mistakenly
-# includes them because of gettext dependencies.
+# We don't need these modules, even though gnulib-tool ordinarily
+# includes them because of dependencies on the modules 'exclude’ and 'regex'.
 avoided_gnulib_modules='
 	--avoid=lock
+	--avoid=mbuiter
+	--avoid=mbuiterf
 '
 
 

gnulib.modules

@@ -63,6 +63,7 @@ lchown
 linkat
 localcharset
 manywarnings
+mcel-prefer
 mkdirat
 mkdtemp
 mkfifoat