Fixes type of dyldInfo for glibc/bionic systems

Darwin and the BSDs define a tagged struct dl_info typedef'd as Dl_info. glibc
and bionic typedef an anonymous struct as Dl_info.
Fixes incorrect #ifs for SJ/LJ exceptions

The was working because, given __APPLE__, _LIBUNWIND_BUILD_SJLJ_APIS was set to
__arm__, but other ARM targets not using SJ/LJ will fail to compile.
Fix virtual class with non-virtual dtor complaint

Fixes compiler complaint about:
src/Unwind/UnwindCursor.hpp:366:25: error: 'libunwind::AbstractUnwindCursor' has virtual functions but non-virtual destructor [-Werror,-Wnon-virtual-dtor]