Add mast and rpl to libcore OWNERS.

Test: build/make/tools/checkowners.py -c libcore/OWNERS
Change-Id: Ib6a5aa710e8b63a853b314081b92c29700481dd1
diff --git a/OWNERS b/OWNERS
index bafe689..2de3abb 100644
--- a/OWNERS
+++ b/OWNERS
@@ -6,11 +6,13 @@
 # People who can approve changes for submission; don't send review emails to them
 # unless you know what you're doing.
 dauletz@google.com
+mast@google.com
 mingaleev@google.com
 nfuller@google.com
 nikitai@google.com
 paulduffin@google.com
 prb@google.com
+rpl@google.com
 vichang@google.com
 
 # Don't send these folks any review emails for this project.