Enable ARM64 compact unwind handling and stub out the ARM64 unwind types.

Issue: PLCR-499
Merge branch 'master' into landonf-PLCR-499-armv8-unwinding
Merge branch 'master' into landonf-PLCR-499-armv8-unwinding
Explicitly write the Mach server implementation to /dev/null; this matches Xcode's MIG target behavior.

Issue: PLCR-497
Bump the version number for 1.2-beta2.
Fix use of TARGET_OS_MAC; iOS also enables this.
Standardize on 64-bit register width; this matches the x86 implementation.

This permits crash reporting on arm64 processes from arm32 host process;
not something we'll need, but it also has the side-benefit of quiescing
a spurious clang tautological comparison warning.
Enable x86-64 builds for the Simulator targets.
Remove the simulator's 'run test' build phase.

In Xcode 5, the standard debug messages that fire when testing error
conditions are all treated as errors when they occur during the build
process.

We'll need to switch over to XCTest eventually, but in the meantime,
this replaces the complex instantiation of the unit tests within the
simulator, and instead matches the behavior to that of the device
tests, where we simply launch the test application directly.
Merge branch 'master' into landonf-PLCR-499-armv8-unwinding
Implement support for ARM64 DWARF, FRAME, and FRAMELESS encodings.

The unit tests validate the encoding as we understand it, but there may
be incompatibilities that remain between the actual in-use CFE encodings
and our implementation, especially as the ARM64 compact unwind
documentation is known to be inaccurate.

The unwinder appears to work against live CFE data, but additional integration
testing of the three encodings will be required prior to merging this
implementation to master.
Mark UNWIND_ARM64_MODE_FRAME_OLD as unsupported.
Centralize handling of the ARM/ARM64 replacement constants.

With the introduction of new processor types and subtypes, Apple often
does not update the system headers on Mac OS X (and the Simulator).
This centralizes replacement compatibility defines (and includes #warnings
that will fire when the SDKs are updated to include the required constants.)
Incomplete checkpoint commit of the unwind test harness, and a sample test.
Add support for running the tests via libunwind; this allows us to verify that our *tests* are themselves correct.

This enables the use of 'verification' mode on arm64 while we implement our
our tests.
Implement working test runner, with compact unwind data.

This has been validated both via libunwind and via our own unwinder.
This commit also replaces the use of a global function symbol with a
simple pointer reference to the target IP to be validated with
unwinding. This avoids any issues caused by the seemingly distinct
functions being re-ordered.

Issue: PLCR-499
Fix computatation of the stack offset and register ordering according to observed behavior.

Issue: PLCR-499
Always enable the libunwind tests where supported.

This providees simultaneous validation of both our custom unwinding
test cases, as well as our unwinder implementation.

Issue: PLCR-499
Implement DWARF unwind data and enable the DWARF tests.

Issue: PLCR-499
Fix copy/paste of incorrect symbol name.

Issue: PLCR-499