client.h: Added specific define to compile the client for Windows

This define specifies the location of the collect-data file that will be
read by the client.

Signed-off-by: Adriano da Luz <al08@c3sl.ufpr.br>
Acked-by: Erik Alexandre Pucci <eap08@c3sl.ufpr.br>
Signed-off-by: Danilo K. S. Yorinori <danilok@c3sl.ufpr.br>