Fix several issues around .ARM.exidx section handling
- Use .ARM.exidx as a fallback unwind plan for non-call site when the instruction emulation based unwind failed.
- Work around an old compiler issue where the compiler isn't sort the entries in .ARM.exidx based on their address.
- Fix unwind info parsing when the virtual file address >= 0x80000000
- Fix bug in unwind info parsing when neither lr nor pc is explicitly restored.