Replace thread_local with a new macro BASE_THREAD_LOCAL. Set this macro to selectively disable thread_local on platforms that don't support it correctly, e.g., Xcode < 8, and gcc < 4.8.3. Progress now uses BASE_THREAD_LOCAL instead of thread_local.

Disable thread_local used in Progress on OS X if Xcode does not support it, since Xcode 7 does not. Progress::Context in turn becomes a static global variable.

Add Progress:Context::set_abort_allowed() which provides a control to turn on/off the abort functionality. Disable the control by default. Add PROGRESS_ALLOW_ABORT to enable abort in a scope. This allows the operation to turn on abort processing only inside exception-handled scopes.

Simplify Progress::Context and Progress::Node and adapt for use in asynchronous tracking and abort requests.

Add Progress::Context to consolidate functionality related to the Progress tracking and aborting features.

Add "aborting" flag to Node to handle cases where the PROGRESS_ABORTED exception is thrown while IPOPT is being executed. Add some extra debugging to the Progress::TrackFunction.

Add tick number counter in Progress::Node. Add Progress::Node track function pointer type. Define the thread-local track function and active node pointers.

Add Progress::Node and support functionality. namespace Progress contains symbols used to track operational progress and facilitate interrupt.

Test::Checksum::Difference now differentiates between complete failure/success and the less important regression/improvement.

Use the error stream to print on the console. This is a trick to avoid polluting the out stream with error messages that can be misinterpreted by ReForm customers. The debug output can be errors or messages, so this is a convenient change, but it is not completely correct. This is related to https://jira.autodesk.com/browse/MTBR-197

Fixes the LocaleSession in such a way to restore the C locale even if the global C++ locale does not have a named. It fixes REFORM-388 and test locale_001.cc.