Audit of English irregulars table

Audited English irregulars table. I found a handful of errors in the
list of stem changes. I also added considerably more doublets using a
combination of intuition and consulting dictionaries (OED, American
Heritage, and Merriam-Webster). The column called "exclude" used to be a
R boolean ("TRUE" or "FALSE"), but now any verb which is a candidate for
exclusion has a non-null string in that cell.