Add support for allocating DMA memory

This patch extends the RAM session interface with the ability to
allocate DMA buffers. The client specifies the type of RAM dataspace to
allocate via the new 'cached' argument of the 'Ram_session::alloc()'
function. By default, 'cached' is true, which correponds to the common
case and the original behavior. When setting 'cached' to 'false', core
takes the precautions needed to register the memory as uncached in the
page table of each process that has the dataspace attached.

Currently, the support for allocating DMA buffers is implemented for
Fiasco.OC only. On x86 platforms, it is generally not needed. But on
platforms with more relaxed cache coherence (such as ARM), user-level
device drivers should always use uncacheable memory for DMA transactions.
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Enable Noux for ARM

With this patch the existing Noux run scripts except the tool chain script
can be executed on the ARM platform.

Fixes #229.
Fix ring buffer interface description

The maximum number of elements in the ring buffer is QUEUE_SIZE - 1.

Fixes #240.
Cross-link terminal

This patch implements a service which allows two clients to communicate
with each other using the 'Terminal' interface.

Fixes #242.
Remove Qemu bug workaround in pl11x driver

Remove a workaround for Qemu <= 0.14.x which results in a wrong
pixel format on Qemu >= 1.0.

Fixes #243.
Noux terminal file system

This patch adds a new "terminal" file system type to Noux, which allows to
create a "character device" file that is connected to a Genode 'Terminal'
service.

The 'Terminal' session created by the file system has the label
"noux(terminal_fs)" to distinguish it from the 'Terminal' session
created by Noux itself.

Fixes #244.
ARM stack alignment

Align the stack on a 16-byte boundary as on the x86_32 platform.

Fixes #236.
libports: Expat

This patch adds the "Expat" XML parser library to libports.

Fixes #245.
Catch 'File_system::Lookup_failed' exception

In 'Fs_file_system::open()' the call of '_fs.dir()' can throw a
'File_system::Lookup_failed' exception, which gets explicitly caught
with this patch.

Fixes #246.
Bunch of compiler warning fixes, issue #234
Use NOVA microkernel from github, add 64bit

Use git to get recent kernels from github. Adjust NOVA patch to compile
with recent github version. Patch and use makefile of NOVA microkernel
to avoid duplicated (and outdated) makefile in Genode

Furthermore, this patch adds support for using NOVA on x86_64. The
generic part of the syscall bindings has been moved to
'base-nova/include/nova/syscall-generic.h'. The 32/64-bit specific
parts are located at 'base-nova/include/32bit/nova/syscalls.h' and
'base-nova/include/64bit/nova/syscalls.h' respectively.

On x86_64, the run environment boots qemu using the Pulsar boot loader
because GRUB legacy does not support booting 64bit ELF executables.

In addition to the NOVA-specific changes in base-nova, this patch
rectifies compile-time warnings or build errors in the 'ports' and
'libports' repositories that are related to NOVA x86_64 (i.e., Vancouver
builds for 32bit only and needed an adaptation to NOVAs changed
bindings)

Fixes #233, fixes #234
NOVA: Improve stability of process destruction

The UTCB of the thread cleaning up thread objects has been unmapped.
However the UTCB of the destroyed thread must be unmapped.

Objects must explicitly be made unreachable before cleaning up. The
server and pager objects must be unreachable before they can be freed.
Both object types are threads. Revoking the thread(EC) cap on NOVA
doesn't mean that the thread stops executing. All portals pointing to a
thread are still reachable by clients even if the last EC cap is gone in
user land. So it must be taken care that no portals are pointing anymore
to a thread when the associated objects are getting destroyed. This
commit handles this.

Additionally, even if the last portal is gone - there can be still an
ongoing request handled by such server/pager object/threads. For each
such object an additional portal is created. This object is called
'cleanup portal' and is only local to the object. After all portals are
revoked the cleanup portal is called. When the call returns we know that
nobody is anymore handled by the object since all remotely available
portals are gone.

Fixes #20
Structures must be dense packed, issue #248

Take care that utcb, hip, crd structure are dense packed by compiler.
Msg_words are 16 bit, adjust bit mask.
Check that typed item fits on UTCB, issue #248

Check that there is enough room for a typed item on the
UTCB. Otherwise deny to add the item and return false.
Enable explicitly a return unused warning to get the right
attention.
Establish mappings during reply, #248

Caller thread sends echo thread mapping information. Echo thread
establish during reply the mappings.

Fixes #248
chroot_loader: Fix run script for 64bit environment

The /lib64 path is required here to allow execution of 64bit binaries.

Here is an example-ldd call:

$ ldd /bin/ls
	linux-vdso.so.1 =>  (0x00007fffdedff000)
	libselinux.so.1 => /lib/x86_64-linux-gnu/libselinux.so.1 (0x00007f4ae207d000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f4ae1e75000)
	libacl.so.1 => /lib/x86_64-linux-gnu/libacl.so.1 (0x00007f4ae1c6c000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f4ae18af000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f4ae16ab000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f4ae22bd000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f4ae148d000)
	libattr.so.1 => /lib/x86_64-linux-gnu/libattr.so.1 (0x00007f4ae1288000)

Fixes #249
Hardening compilation support for 64bit Linux

Without this patch the compilation failed with:

/usr/bin/ld: main.o: relocation R_X86_64_32S against
`vtable for Genode::Dataspace' can not be used when making a shared object;
recompile with -fPIC
main.o: could not read symbols: Bad value
collect2: ld returned 1 exit status
make[6]: *** [init] Error 1

For this patch the use of the hardening tool chain must be indicated
using the "hardening_tool_chain" SPECS entry within the file
<build>/etc/specs.conf

Fixes #79
Fix US layout

The right bracket used the wrong character and the "pipe" was missing.

Fixes #241.