FORTIFY_SOURCE: add umask check

Verify that the call to umask makes sense. While this wouldn't
have detected bug 7094213 (because the low order bits were all zero),
it might detect other similar bugs.

References: https://code.google.com/p/android-source-browsing/source/detail?r=acba45cc4b1f98f67fcdeda2f7c13ed57659b92a&repo=platform--libcore

Change-Id: I966a531d6b3cf8e1c5eacd69bd3cbec475b5fa58
3 files changed