add an internationalization constant

gather all ENGLISH|GERMAN|CHINESE etc preprocessor hell into a single
library, so to restrict the number of targets that need to be built 8x

this still has UB/EDITOR definitions so that still needs to be dealt
with before we can build it only 8 times

i18n/include/language.hpp

@@ -0,0 +1,17 @@
+#pragma once
+
+namespace i18n {
+enum class Lang
+{
+  en,
+  de,
+  ru,
+  nl,
+  pl,
+  fr,
+  it,
+  zh
+};
+}
+
+extern const i18n::Lang g_lang;