Reserve space in pthread structures for future extensibility.

Make our structures equal in size with glibc structures. This should
give us plenty of space to implement any missing feature.

Bug: 13278744
Bug: 12875898
Change-Id: I980017fd5942411ebc5ac32b2673a10a20db68c8
Merge "Reserve space in pthread structures for future extensibility."
Removed non-existing include dir

Change-Id: I3e00a8471e6d94f596a34bdfdb26a0caba23dd82
Merge "Removed non-existing include dir"
Remove an unsed include dir

Change-Id: I05aa1e7e0639a5ec5576bf7646f35d2e5b157c09
Merge "Remove an unsed include dir"
auto-merger: merge in from aosp/master