maint: prefer mcel

* bootstrap.conf (gnulib_modules): Add mcel-prefer.
(gnulib_tool_option_extras): Avoid mbiterf.
This simplifies Bison a bit, which does not need
the more-complex mbiterf.

bootstrap.conf

@@ -34,6 +34,7 @@ gnulib_modules='
   libtextstyle-optional
   linked-list
   malloc-gnu
+  mcel-prefer
   mbfile mbswidth
   obstack
   obstack-printf
@@ -80,7 +81,16 @@ XGETTEXT_OPTIONS_RUNTIME=$XGETTEXT_OPTIONS'\\\
  --keyword=YY_ \\\
 '
 
-gnulib_tool_option_extras='--symlink --conditional-dependencies --makefile-name=gnulib.mk --automake-subdir --automake-subdir-tests --po-base=gnulib-po --po-domain=bison'
+gnulib_tool_option_extras="\
+ --automake-subdir\
+ --automake-subdir-tests\
+ --avoid=mbiterf\
+ --conditional-dependencies\
+ --makefile-name=gnulib.mk\
+ --po-base=gnulib-po\
+ --po-domain=bison\
+ --symlink\
+"
 
 gnulib_extra_files="$gnulib_extra_files build-aux/move-if-change"