kernel: add a compatibility commpage on x86_64.

* x86 uses a commpage with 32-bit addresses, incompatible with the one used for
x86_64. For this reason, a compatibility commpage is needed to support a 32-bit
userland on x86_64.
* define ADDRESS_TYPE as a macro for addr_t (default) or uint32 (for the 32-bit
commpage).
* team_create_thread_start_internal() will use clone_commpage_area() with
KERNEL_USER_DATA_BASE or clone_commpage_compat_area() with
KERNEL_USER32_DATA_BASE, to setup the correct commpage.
* real_time_clock (in compatibility mode) also updates the compatibility
commpage with real time data.

Change-Id: I61605077ce0beabab4439ef54edd1eae26f26fd2

* Introduced new header directory headers/private/system which is supposed
to contain headers shared by kernel and userland (mainly libroot).
* Moved quite a few private kernel headers to the new location. Split
several kernel headers into a shared part and one that is still kernel
private. Adjusted all affected Jamfiles and source in the standard x86
build accordingly. The build for other architectures and for test code
may be broken.
* Quite a bit of userland code still includes private kernel headers.
Mostly those are <util/*> headers. The ones that aren't strictly
kernel-only should be moved to some other place (maybe
headers/private/shared/util).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25486 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Introduced new header directory headers/private/system which is supposed
to contain headers shared by kernel and userland (mainly libroot).
* Moved quite a few private kernel headers to the new location. Split
several kernel headers into a shared part and one that is still kernel
private. Adjusted all affected Jamfiles and source in the standard x86
build accordingly. The build for other architectures and for test code
may be broken.
* Quite a bit of userland code still includes private kernel headers.
Mostly those are <util/*> headers. The ones that aren't strictly
kernel-only should be moved to some other place (maybe
headers/private/shared/util).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25486 a95241bf-73f2-0310-859d-f6bbb57e9c96