aarch32: Move tpidruro from vcpu to tcb context

This register is visible to software executing at PL0 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 PL0.

This also fixes a 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.

Signed-off-by: Kent McLeod <Kent.Mcleod@data61.csiro.au>

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

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.

libsel4/arm: Move VCPU to the common interface

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

manual: Trivial whitespace

update #ifdef to #if in auto generated files

arm-hyp: Add conditions to invocations

Correct merge of master

Modify Kconfig and Makefile for aach32 as sel4_arch
libsel4: updates to include aarch32 as sel4_arch