pmwebapi: do best-effort error-message printing for pmwebapi errors
pmwebapi: do best-effort error-message printing for pmwebapi errors

* pmwebapi.c (pmwebapi_notify_error): New function.  Call it from the other
  REST methods' failure paths.

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