Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

trivial: arm: Improve object method docs

aarch64: Fix seL4_ARM_PageDirectory interface doc

It is passed a vspace cap not an upper page directory cap

aarch64: Move tpidrro_el0 from vcpu to tcb context

This register is visible to software executing at EL0 but not writeable.
Storing it in the VCPU context required custom save/restore handling as
it had to be explicitly handled when switching from a VCPU thread to a
non-VCPU thread so that it didn't become a channel. It is possible to
now update this register via seL4_TCB_WriteRegisters for software
executing at EL0.

This also fixes a potential bug where if a vcpu-thread is switched for a
non-vcpu-thread and then switched to a different vcpu-thread the
original vcpu-thread's copy of this register will get set to 0.

aarch64: add support for 40-bit PA

This commit adds support for using a 40-bit physical addresses in
aarch64-hyp mode.

40-bit PA support is implemented by using a 3-stage translation, with a
13 bit page upper directory as the vspace root. PageGlobalDirectories
are not used in this configuration.

To use 40-bit PAs, platforms should set KernelArmPASizeBits40 to ON.

Co-authored-by: Yanyan Shen <yanyan.shen@data61.csiro.au>
Co-authored-by: Chris Guikema <chris.guikema@dornerworks.com>

aarch64: abstract vspace in libsel4

Depending on the physical address range the top level translation table
may be a page upper directory or a page global directory. Rename in
libsel4 the invocations on top level structures to be on an
seL4_ARM_VSpace rather than an seL4_ARM_PageGlobalDirectory.

RFC-3: Update user context for ARM with thread IDs

Switched appropriate naming conventions.
Was using the aarch64, have switched to aarch64 names.

TIPDRURW -> tpidr_el0
TPIDRURO -> tpidrro_el0
TPIDRPRW -> tpidr_el1

Switch TLS register on aarch32 from TPIDURO (tpidrro_el0) to tpidr_ro so
that it can be written to from user-land.

Thread ID registers tpidr_el0 have been added to the user context for
aarch32 and aarch64.

Only the thread ID that is writeable from EL0 is saved in the TCB and
saved/restored on context switch.

Thread IDs that are only changed within a VM (the read-only thread ID
for exception level 0 and the thread ID for exception level 1) are
stored in the VCPU and saved and stored as part of VM enable/disable.

Thread IDs that are only changed with VMs have been separated out into
hypervisor code.

manual: Added <docref> XML Tag to Doxygen

Introduced a new Doxygen XML tag '<docref>'. The intention of
this tag is to indicate a section of text in the Doxygen XML that
will contain a reference to another section in the Manual e.g.
"See \autoref<sec:x>". As other generation formats aren't aware of
other chapters/sections in the manual, the <docref> encapsulation
allows it to omit the text from the output. The Latex generator
has been modified to continue parsing the 'docref' contents.

Manual: document mode/arm object invocations

libsel4: fix licenses

- some were incorrectly marked GPL (libsel4 is BSD)
- update NICTA --> DATA61 etc
- fix tags D61 --> DATA61
- update year to 2017

manual: Friendly names for arch-specific methods

manual: Add basic names and labels to interfaces

aarch64: Add aarch64 libsel4 implementation