Use "concatenatable" language codes

Marlin/Configuration.h

@@ -1580,10 +1580,10 @@
  *
  * Select the language to display on the LCD. These languages are available:
  *
- *   en, an, bg, ca, cz, da, de, el, el-gr, es, eu, fi, fr, gl, hr, it, jp-kana,
- *   ko_KR, nl, pl, pt, pt-br, ru, sk, tr, uk, vi, zh_CN, zh_TW, test
+ *   en, an, bg, ca, cz, da, de, el, el_gr, es, eu, fi, fr, gl, hr, it, jp_kana,
+ *   ko_KR, nl, pl, pt, pt_br, ru, sk, tr, uk, vi, zh_CN, zh_TW, test
  *
- * :{ 'en':'English', 'an':'Aragonese', 'bg':'Bulgarian', 'ca':'Catalan', 'cz':'Czech', 'da':'Danish', 'de':'German', 'el':'Greek', 'el-gr':'Greek (Greece)', 'es':'Spanish', 'eu':'Basque-Euskera', 'fi':'Finnish', 'fr':'French', 'gl':'Galician', 'hr':'Croatian', 'it':'Italian', 'jp-kana':'Japanese', 'ko_KR':'Korean (South Korea)', 'nl':'Dutch', 'pl':'Polish', 'pt':'Portuguese', 'pt-br':'Portuguese (Brazilian)', 'ru':'Russian', 'sk':'Slovak', 'tr':'Turkish', 'uk':'Ukrainian', 'vi':'Vietnamese', 'zh_CN':'Chinese (Simplified)', 'zh_TW':'Chinese (Traditional)', 'test':'TEST' }
+ * :{ 'en':'English', 'an':'Aragonese', 'bg':'Bulgarian', 'ca':'Catalan', 'cz':'Czech', 'da':'Danish', 'de':'German', 'el':'Greek', 'el_gr':'Greek (Greece)', 'es':'Spanish', 'eu':'Basque-Euskera', 'fi':'Finnish', 'fr':'French', 'gl':'Galician', 'hr':'Croatian', 'it':'Italian', 'jp_kana':'Japanese', 'ko_KR':'Korean (South Korea)', 'nl':'Dutch', 'pl':'Polish', 'pt':'Portuguese', 'pt_br':'Portuguese (Brazilian)', 'ru':'Russian', 'sk':'Slovak', 'tr':'Turkish', 'uk':'Ukrainian', 'vi':'Vietnamese', 'zh_CN':'Chinese (Simplified)', 'zh_TW':'Chinese (Traditional)', 'test':'TEST' }
  */
 #define LCD_LANGUAGE en
 

Marlin/src/core/language.h

@@ -49,7 +49,7 @@
 // da         Danish
 // de         German
 // el         Greek
-// el-gr      Greek (Greece)
+// el_gr      Greek (Greece)
 // en         English
 // es         Spanish
 // eu         Basque-Euskera
@@ -58,12 +58,12 @@
 // gl         Galician
 // hr         Croatian
 // it         Italian
-// jp-kana    Japanese
+// jp_kana    Japanese
 // ko_KR      Korean (South Korea)
 // nl         Dutch
 // pl         Polish
 // pt         Portuguese
-// pt-br      Portuguese (Brazilian)
+// pt_br      Portuguese (Brazilian)
 // ru         Russian
 // sk         Slovak
 // tr         Turkish