Minor fix to Flags to make it trivially pickle-able, and by extension, most fields and forms.
Minor fix to Flags to make it trivially pickle-able, and by extension, most
fields and forms.

Xender/wtforms,Aaron1992/wtforms,pawl/wtforms,hsum/wtforms,pawl/wtforms,jmagnusson/wtforms,skytreader/wtforms,wtforms/wtforms,cklein/wtforms,subyraman/wtforms,Aaron1992/wtforms,crast/wtforms