Separated dfs pipe into implementation and interface modules.

Separated dfs pipe into implementation and interface modules.
rpc_parse/parse_dfs.c: Had to add buffer overrun checking ! HOW DID THIS GET IN HERE !
rpc_parse/parse_prs.c: Ensure prs_alloc_mem does a memset of zero before returning.
Jeremy.
(This used to be commit c9a6a17025f4a6850cd2b9a9ddb48bdeec8b3ffe)