Log Message:
Update to 1.81

Upstream changes:
revision 1.81  2014-10-25
----------------------------
    - Fix overly-enthusiastic parenthesis unroller (RT#99503)

revision 1.80  2014-10-05
----------------------------
    - Fix erroneous behavior of is_literal_value($) wrt { -ident => ... }
    - Explicitly croak on top-level special ops (they didn't work anyway)

revision 1.79  2014-09-25
----------------------------
    - New exportable functions: is_literal_value($) and is_plain_value($)
    - New attribute 'escape_char' allowing for proper escape of quote_chars
      present in an identifier
    - Deprecate { "" => \... } constructs
    - Treat { -value => undef } as plain undef in all cases
    - Explicitly throw on { -ident => undef }