Add SymbolicConstantsMach and its test

util/mach/mach_extensions.h

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 49 matching lines @@
 //! Callers can use this function in preference to `mach_thread_self()`. This
 //! function returns an extant reference to the current thread’s port without
 //! incrementing its reference count.
 //!
 //! \return The value of `mach_thread_self()` without incrementing its reference
 //!     count. The returned port must not be deallocated by
 //!     `mach_port_deallocate()`. The returned value is valid as long as the
 //!     thread continues to exist as a `pthread_t`.
 mach_port_t MachThreadSelf();
 
+//! \brief The value for `EXC_MASK_ALL` appropriate for the operating system at
+//!     run time.
+//!
+//! The SDK’s definition of `EXC_MASK_ALL` has changed over time, with later
+//! versions containing more bits set than earlier versions. However, older
+//! kernels will reject exception masks that contain bits set that they don’t
+//! recognize. Calling this function will return a value for `EXC_MASK_ALL`
+//! appropriate for the system at run time.
+//!
+//! \note `EXC_MASK_ALL` does not include the value of `EXC_MASK_CRASH`.
+exception_mask_t ExcMaskAll();
+
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_MACH_MACH_EXTENSIONS_H_