Drop the branch-specific version number in preparation of merge.
Fix comment typo.

Issue: PLCR-495
Fix leak of plcrash_async_macho_string_t instance.

Issue: PLCR-495
Add missing byteswap.

Issue: PLCR-495
Convert the remaining uses of PLCRASH_EINVAL to PLCRASH_EINVALID_DATA.

Issue: PLCR-495
Merge branch 'master' into landonf-PLCR-499-armv8-unwinding