Change the simple-minded stack walk to not depend on lldb to unwind
the first frame.
Collect a list of Modules and Addresses seen while backtracing (with
both methods), display the image list output for all of those modules,
plus disassemble and image show-unwind any additional frames that
the simple backtrace was able to unwind through instead of just the
lldb unwind algorithm frames.
Remove checks for older lldb's that didn't support -a for disassemble
or specifying the assembler syntax on x86 targets.
llvm-svn: 184280