[sanitizer] Move stat/__xstat to the common interceptors

Summary:
Adds stat/__xstat to the common interceptors.

Removes the now-duplicate stat/__xstat interceptor from msan/tsan/esan.
This adds stat/__xstat to asan, which previously did not intercept it.

Reviewers: aizatsky, eugenis

Subscribers: tberghammer, danalbert, srhines, kubabrecka, llvm-commits, vitalybuka, eugenis, kcc, bruening

Differential Revision: http://reviews.llvm.org/D19875

llvm-svn: 268440