RPCRT4: Fix compiler warning

[Hans Leidekker]

GCC 3.3.3 spews 511 of these during a full compile of Wine:

 warning: use of cast expressions as lvalues is deprecated

Should probably become a janitorial task, but here's one fixed already.

Changelog:
  Fix compiler warning.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: rpcrt4_cproxy_c.diff
Type: text/x-diff
Size: 581 bytes
Desc: not available
Url : http://www.winehq.org/pipermail/wine-patches/attachments/20040418/37b77879/rpcrt4_cproxy_c.bin