Fix integer sizing issues in the NetworkIO Meter

On Linux kernels the size of the values exported for network
device bytes and packets has used a 64 bit integer for quite
some time (2.6+ IIRC).  Make the procfs value extraction use
correct types and change internal types used to rate convert
these counters (within the NetworkIO Meter) 64 bit integers,
where appropriate.

dragonflybsd/Platform.c

@@ -233,15 +233,9 @@ bool Platform_getDiskIO(DiskIOData* data) {
    return false;
 }
 
-bool Platform_getNetworkIO(unsigned long int* bytesReceived,
-                           unsigned long int* packetsReceived,
-                           unsigned long int* bytesTransmitted,
-                           unsigned long int* packetsTransmitted) {
+bool Platform_getNetworkIO(NetworkIOData* data) {
    // TODO
-   *bytesReceived = 0;
-   *packetsReceived = 0;
-   *bytesTransmitted = 0;
-   *packetsTransmitted = 0;
+   (void)data;
    return false;
 }