Constify some things in preparation for CodeGenSubRegIndex to be stored by value in their container, removing the indirection
Use deque<T> rather than vector<T*> since it provides the same invalidation semantics (at least when removal is not needed) without the extra indirection/ownership complexity

Order matters for this container, it seems (using a forward_list and
replacing the original push_backs with emplace_fronts caused test
failures). I didn't look too deeply into why.

(& in retrospect, I might go back & change some of the forward_lists I
introduced to deques anyway - since most don't require removal, deque is
a more memory-friendly data structure (moderate locality while not
invalidating pointers))
The finishing touches on getting the compact unwind dumping completed
for x86_64.  i386, arm, arm64 aren't handled yet but those are minor
variations on this format.

This commit also adds code to read the symbol table out of the
binary and read the LC_FUNCTION_STARTS to augment the symbol table
with the start addresses of all the functions - and print the
function names when showing the unwind info.