x86_64: make all targets compile

Signed-off-by: Reto Achermann <reto.achermann@inf.ethz.ch>

replacing umlaute and fixing address in headers Haldeneggsteig -> Universitaetsstrasse

Signed-off-by: Reto Achermann <reto.achermann@inf.ethz.ch>

Added support for a basic pthread barrier

Signed-off-by: Jana Giceva <gicevaj@inf.ethz.ch>
Signed-off-by: Gerd Zellweger <mail@gerdzellweger.com>

posixcompat: make pthread_once a wrapper over the version in libbarrelfish

Summary:
Both the pthread and native versions now share a single common
implementation (added in D9). The new approach should also be faster
since it avoids a full mutex and instead only has to consult the
per-thread epoch on the common path. I should note, I have not run
any benchmarks to confirm this and may be wrong.

Test Plan: Compiles but have not validated more thoroughly.

Differential Revision: https://code.systems.ethz.ch/D12

Signed-off-by: Zaheer Chothia <zchothia@inf.ethz.ch>

Implemented newlib __lock_* functions for Barrelfish.

Among other things this change enables proper locking for printf and co in
multithreaded programs.

headers: remove C99 designated initializers; not supported by C++.

Only looked at header files in //include. Matches were found with:
$ ack --hh '(?<!\w)\.\w+\s*\='

Merge from ASPLOS tree.