If 'property' is conditional property, returns
        condition and the property, e.g
        <variant>debug,<toolset>gcc:<inlining>full will become
        <variant>debug,<toolset>gcc <inlining>full.
        Otherwise, returns empty string.

def split_conditional (property):
    """ If 'property' is conditional property, returns
        condition and the property, e.g
        <variant>debug,<toolset>gcc:<inlining>full will become
        <variant>debug,<toolset>gcc <inlining>full.
        Otherwise, returns empty string.
    """
    assert isinstance(property, basestring)
    m = __re_split_conditional.match (property)

    if m:
        return (m.group (1), '<' + m.group (2))

    return None