libmeminfo: add active / inactive / unreclaimable to meminfo fields

Parses additional fields from /proc/meminfo.
They will be used in the calculation of unaccounted system memory
(essentially we consider them accounted for - these are the pages used
by the union of userspace processes + page cache)

Bug: 172201884
Test: libmeminfo_test
Change-Id: I8dc92d9a44495a3b95ac8d9b915ab9cfb1115f4d
2 files changed