x86: Dangerous read/write MSR interface

Provides a syscall interface for reading and writing arbitrary MSR values. This is
being introduced as an alternative to the DebugRun, as the main purpose of debug run
is for modifying the performance monitoring events via read/write MSR.

libsel4: Remove unused argument in seL4_VMEnter syscall

This VCPU argument does not make sense given semantics of the VMEnter syscall,
and as a result the argument is ignored by the kernel.

libsel4: fix licenses

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

seL4_DebugDumpScheduler: remove unused argument

SELFOUR-880: add seL4_DebugDumpScheduler

- when CONFIG_DEBUG is enabled, track all threads
- when CONFIG_PRINTING is enabled, provide seL4_DebugDumpScheduler which
allows the user to dump the state of the kernel scheduler.

SELFOUR-862: CONFIG_PRINTING --> seL4_DebugPutChar

seL4_DebugPutChar is only available when CONFIG_PRINTING is enabled

libsel4: fix warning in seL4_BenchmarkSetLogBuffer

x64: implement seL4_BenchmarkFlushCaches

by moving the ia32 implementation up a level to x86
and implementing the syscall stub.

Modify FinalizeLog syscall

There is no way to know how many entries the syscall log contains
otherwise. One option was iterating through until finding a 0
terminator, however this requires the log to be zeroed before each
trial. This changes the FinalizeLog syscall to return the number of
entries.

Change debug #ifdefs to be from autoconf.h

Previously the #ifdefs for some debug syscalls relied on definitions
from Makefile.flags in sel4_tools. This changes them to use configs
defined in autoconf.h which makes them easier to import when building
projects that don't use sel4_tools.

s/D61/DATA61/ in license headers for consistency

libsel4: seL4_VMEnter syscall for x86-64

libsel4: Optional public symbols for external interfaces

CONFIG_LIB_SEL4_PUBLIC_SYMBOLS=y will disable inlining for external
interfaces (except deprecated functions), thereby providing public
symbols for easy linkage with other languages.

SELFOUR-675: x64: Increase message registers from 2 to 4

Replace #pragma once with include guards

Trivial: correct x86_64 seL4_BenchmarkReset() return value

[STYLE_FIX]

x64/libsel4: Add x64 libsel4 implementation