Strip never-translated strings from language files

Marlin/language_an.h

Marlin/language_bg.h

Marlin/language_ca.h

Marlin/language_cn.h

Marlin/language_cz.h

Marlin/language_da.h

Marlin/language_de.h

Marlin/language_el-gr.h

Marlin/language_el.h

Marlin/language_en.h

Marlin/language_es.h

Marlin/language_eu.h

Marlin/language_fi.h

Marlin/language_fr.h

Marlin/language_gl.h

Marlin/language_hr.h

Marlin/language_it.h

Marlin/language_kana.h

Marlin/language_kana_utf8.h

Marlin/language_nl.h