fix PageList API arg passing to GeneratorList
fix PageList API arg passing to GeneratorList

PageList wasn't adding the 'g' prefix to API arguments it
passes to GeneratorList, and GeneratorList doesn't do that
itself. This fixes it.

mwclient/mwclient,PierreSelim/mwclient,ubibene/mwclient,AdamWill/mwclient,Jobava/mirror-mwclient,JeroenDeDauw/mwclient,danmichaelo/mwclient