Prefer straight quotes in random script files, as they are not converted.
Prefer grave quotes in a couple of places in the manual that were missed
earlier, as these quotes are converted.
* lisp/loadup.el: Explicitly load cp51932 and eucjp-ms.
* lisp/language/japanese.el: Use require rather than load.
* lisp/international/cp51932.el, lisp/international/eucjp-ms.el:
Provide a feature.
* admin/charsets/eucjp-ms.awk, admin/charsets/cp51932.awk:
Provide a feature in the generated file.