[DCCP]: Debug timeval operations

Problem:

 Most target types in the CCID3 code are u32, so subtle conversion errors
 can occur if signed time calculations yield negative results: the original
 values are lost in the conversion to unsigned, calculation errors go undetected.

 This patch therefore
   * sets all critical time types from unsigned to suseconds_t
   * avoids comparison between signed/unsigned via type-casting
   * provides ample warning messages in case time calculations are negative

 These warning messages can be removed at a later stage when the code
 has undergone more testing.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 44829d6..a0900bf 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -432,6 +432,7 @@
 		tv->tv_sec--;
 		tv->tv_usec += USEC_PER_SEC;
 	}
+	DCCP_BUG_ON(tv->tv_sec < 0);
 }
 
 #ifdef CONFIG_SYSCTL