Added support for line-based comments.

--HG--
branch : trunk
diff --git a/jinja2/defaults.py b/jinja2/defaults.py
index b1a2f6a..458485e 100644
--- a/jinja2/defaults.py
+++ b/jinja2/defaults.py
@@ -19,6 +19,7 @@
 COMMENT_START_STRING = '{#'
 COMMENT_END_STRING = '#}'
 LINE_STATEMENT_PREFIX = None
+LINE_COMMENT_PREFIX = None
 TRIM_BLOCKS = False
 NEWLINE_SEQUENCE = '\n'