Linux changed this behavior in 16e72e9b30986ee15f17fbb68189ca842c32af58
(v4.11). Previously, extra pages were always mapped RW. Now, those pages will
be executable if the segment specified PF_X. They still must be writeable.
PiperOrigin-RevId: 272256280
Based on the guidelines at
https://opensource.google.com/docs/releasing/authors/.
1. $ rg -l "Google LLC" | xargs sed -i 's/Google LLC.*/The gVisor Authors./'
2. Manual fixup of "Google Inc" references.
3. Add AUTHORS file. Authors may request to be added to this file.
4. Point netstack AUTHORS to gVisor AUTHORS. Drop CONTRIBUTORS.
Fixes#209
PiperOrigin-RevId: 245823212
Change-Id: I64530b24ad021a7d683137459cafc510f5ee1de9