parsers.c: parse_manifest: fixing refcount of flags
When flags was DECREF'ed, scope was referencing to the outer variable,
outside of the block.
It was in fact always NULL: the real Python object was never decref'ed.
adding foo
% no signatures
% hg sign 0
Signing 0:e63c23eaa88a
% hg sigs
hgtest 0:e63c23eaa88ae77967edcf4ea194d31167c478b0
% hg sigcheck 0
e63c23eaa88a is signed by:
hgtest