After freeing a value set pointer, set it to NULL for realloc.
After freeing a value set pointer, set it to NULL for realloc.

This was causing havoc in the Windows PMDA under Windows Server
2008, as random memory corruption would result in realloc.

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