Unknown process states are expected since libprocinfo doesn't
list all process states in
https://github.com/torvalds/linux/blob/master/fs/proc/array.c#L130.
So remove error message for unknown state.
Bug: none
Test: run libprocinfo_test.
Change-Id: I321893855235367e037afd58ccb63d5140619095
Add a new library for parsing /proc files. Start with helpers for
parsing /proc/<pid>/status and /proc/<pid>/task.
Bug: http://b/30705528
Test: libprocinfo_test32/64 on host/bullhead
Change-Id: I5757514c0aede8a9d75834b55aae42a5cf762b95