replace with actual_{free,used} fields so we can portably adjust
-/+ buffers/cache on linux and perhaps on other platforms w/ different
semantics.
		
	
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|---|---|---|
| .. | ||
| sigar_fileinfo.h | ||
| sigar_getline.h | ||
| sigar_log.h | ||
| sigar_private.h | ||
| sigar_util.h | ||
| sigar.h | ||