[scudo] Add some logs for Android

Summary:
Namely, set the abort message, and allow to write the message to syslog if the
option is enabled.

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D48902

llvm-svn: 336445