Basic fetch callback methods are now working in python PMDA module
Basic fetch callback methods are now working in python PMDA module

Fixes up the way the tuple returned from the fetch callback is parsed
back in the C code (before interfacing to libpcp_pmda), adds numerous
additional checks and diagnostics to the python return values / error
code, and removes some leftover debug code from earlier commits.

prasincs/pcp,tjanez/pcp,aeg-aeg/pcpfans,mbaldessari/pcp,prasincs/pcp,prasincs/pcp,aeg-aeg/pcpfans,edwardt/pcp,mbaldessari/pcp,prasincs/pcp,tjanez/pcp,prasincs/pcp,wuliming/pcp,wuliming/pcp,wuliming/pcp,edwardt/pcp,prasincs/pcp,tjanez/pcp,andyvand/cygpcpfans,mbaldessari/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,andyvand/cygpcpfans,adfernandes/pcp,andyvand/cygpcpfans,tjanez/pcp,andyvand/cygpcpfans,adfernandes/pcp,tjanez/pcp,edwardt/pcp,andyvand/cygpcpfans,prasincs/pcp,adfernandes/pcp,aeg-aeg/pcpfans,adfernandes/pcp,wuliming/pcp,andyvand/cygpcpfans,wuliming/pcp,tjanez/pcp,andyvand/cygpcpfans,mbaldessari/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,andyvand/cygpcpfans,aeg-aeg/pcpfans,edwardt/pcp,edwardt/pcp,tjanez/pcp,wuliming/pcp,wuliming/pcp,adfernandes/pcp,mbaldessari/pcp,mbaldessari/pcp,edwardt/pcp,tjanez/pcp,prasincs/pcp,edwardt/pcp,aeg-aeg/pcpfans,wuliming/pcp,edwardt/pcp,aeg-aeg/pcpfans