Revert "FreeBSD also uses these structs so do not hide them"
Revert "FreeBSD also uses these structs so do not hide them"

This reverts commit e07b43c02d5cf1ea060c018fdf2e2ad34b7c7d80.

See pull #344

libunwind/libunwind,libunwind/libunwind,libunwind/libunwind