This reverts commit adc675c8ef55b59bb2facf795a3c26411cfbf3ed. The original commit added support for a non-standard libunwind API, so it was not of general utility.
This reverts commit adc675c8ef55b59bb2facf795a3c26411cfbf3ed. The original commit added support for a non-standard libunwind API, so it was not of general utility.