r7161: - Add support for "aliases" for pidls scalar types and add a few aliases.

r7161: - Add support for "aliases" for pidls scalar types and add a few aliases.
- Define __PIDL__ when preprocessing IDL files.
- Remove a couple of useless defines from rpcecho.idl
rpcecho.idl now works in both pidl and midl
(althought pidl is a bit pedantic and gives two warnings)
(This used to be commit 6731e0a6548ac24d561ba48c8e9611d0034e662f)