avoid executing startup file twice when using run-octave script (bug #45872) * site-rcfile: Rename from local-rcfile. * version-rcfile: Rename from main-rcfile. * scripts/startup/module.mk: Update to match new names. (install-startup-files, uninstall-startup-files): Move rules here from scripts/module.mk. * site-rcfile, version-rcfile: Note environment variables that may be used to select site and version rcfiles to execute. * run-octave.in (OCTAVE_VERSION_INITFILE): Define to use version-rcfile from source tree. (OCTAVE_SITE_INITFILE): Update to use site-rcfile from source tree.