fix line accounting in multi-line strings (#3752)

fixes #3748

lib/parse.js

@@ -241,16 +241,16 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
         if (signal_eof && !ch)
             throw EX_EOF;
         if (NEWLINE_CHARS[ch]) {
-            S.newline_before = S.newline_before || !in_string;
-            ++S.line;
             S.col = 0;
-            if (!in_string && ch == "\r" && peek() == "\n") {
-                // treat a \r\n sequence as a single \n
-                ++S.pos;
+            S.line++;
+            if (!in_string) S.newline_before = true;
+            if (ch == "\r" && peek() == "\n") {
+                // treat `\r\n` as `\n`
+                S.pos++;
                 ch = "\n";
             }
         } else {
-            ++S.col;
+            S.col++;
         }
         return ch;
     }