Revert "parser: simplify :skip_lines implementation"

This reverts commit c2cc984.

This may cause invalid parse result.

Author: kou

lib/csv/parser.rb

@@ -901,15 +901,18 @@ def build_scanner
     def skip_needless_lines
       return unless @skip_lines
 
-      @scanner.keep_start
-      @scanner.each_line(@row_separator) do |line|
-        line << @row_separator if parse_row_end
-        break unless skip_line?(line)
-        @lineno += 1
-        @scanner.keep_drop
+      until @scanner.eos?
         @scanner.keep_start
+        line = @scanner.scan_all(@not_line_end) || "".encode(@encoding)
+        line << @row_separator if parse_row_end
+        if skip_line?(line)
+          @lineno += 1
+          @scanner.keep_drop
+        else
+          @scanner.keep_back
+          return
+        end
       end
-      @scanner.keep_back
     end
 
     def skip_line?(line)