Avoid implicit fallthrough, by duplicating code (#4556)

The cleverness is probably not worth it.

source/text_handler.cpp

@@ -120,7 +120,8 @@ spv_result_t getWord(spv_text text, spv_position position, std::string* word) {
         case '\n':
         case '\r':
           if (escaping || quoting) break;
-        // Fall through.
+          word->assign(text->str + start_index, text->str + position->index);
+          return SPV_SUCCESS;
         case '\0': {  // NOTE: End of word found!
           word->assign(text->str + start_index, text->str + position->index);
           return SPV_SUCCESS;