Add librank2

Identical with librank, but written using libmeminfo.

Bug: 114325007
Bug: 111694435
Test: librank2
Test: librank2 -m rx
Test: librank2 -m rx -P /system/lib64
Test: librank2 -u -P /system/lib
Test: librank2 -R -m rx

Change-Id: Ib6ecb601a0b6ecb5b4b75285f772586e05ae388a
Signed-off-by: Sandeep Patil <sspatil@google.com>