fix bug in sigar_disk_usage_get and change counter index

[D3Hunter]

some fields such as 'Disk Time' are 64bit long

changed counter index of following values
/* % Disk Time /
/ % Disk Read Time /
/ % Disk Write Time */

This is what i got with tools from https://msdn.microsoft.com/en-us/library/windows/desktop/aa372138(v=vs.85).aspx :

236 LogicalDisk
_Total
C:
HarddiskVolume1

408 % Free Space
226 Avg. Disk Bytes/Read
224 Avg. Disk Bytes/Transfer
228 Avg. Disk Bytes/Write
1400 Avg. Disk Queue Length   -------equals to "200"
1402 Avg. Disk Read Queue Length -------equals to "202"
208 Avg. Disk sec/Read
206 Avg. Disk sec/Transfer
210 Avg. Disk sec/Write
1404 Avg. Disk Write Queue Length -------equals to "204"
198 Current Disk Queue Length
218 Disk Bytes/sec
220 Disk Read Bytes/sec
214 Disk Reads/sec
212 Disk Transfers/sec
222 Disk Write Bytes/sec
216 Disk Writes/sec
410 Free Megabytes
1484 Split IO/Sec