Update upstream libbacktrace sources

[krlmlr]

Currently vendored from my fork's main branch: https://github.com/krlmlr/libbacktrace.

[barracuda156]

macho sources are more complete here: https://github.com/ianlancetaylor/libbacktrace/blob/master/macho.c

[krlmlr]

Thanks. I just synced my fork, is it better now?

[barracuda156]

Apparently that is not sufficient, something else has to be fixed too. I pulled over an updated repo, but:

* checking examples ... ERROR
Running examples in ‘winch-Ex.R’ failed
The error most likely occurred in:

> ### Name: winch_trace_back
> ### Title: Native stack trace
> ### Aliases: winch_trace_back
> 
> ### ** Examples
> 
> ## Don't show: 
> if (winch_available()) (if (getRversion() >= "3.4") withAutoprint else force)({ # examplesIf
+ ## End(Don't show)
+ winch_trace_back()
+ 
+ foo <- function() {
+   winch_call(bar)
+ }
+ 
+ bar <- function() {
+   winch_trace_back()
+ }
+ 
+ foo()
+ ## Don't show: 
+ }) # examplesIf
> winch_trace_back()
Error in winch_trace_back() : unw_getcontext() error: -1073785400
Calls: <Anonymous> ... source -> withVisible -> eval -> eval -> winch_trace_back
Execution halted
* checking for unstated dependencies in ‘tests’ ... OK
* checking tests ...
  Running ‘example0.R’
 ERROR
Running the tests in ‘tests/example0.R’ failed.
Last 13 lines of output:
  > 
  > bar0 <- function() {
  +   winch_call(baz0)
  + }
  > 
  > baz0 <- function() {
  +   winch_trace_back()
  + }
  > 
  > if (winch_available()) {
  +   foo0()
  + }
  Error in winch_trace_back() : unw_getcontext() error: -1073785320
  Calls: foo0 ... <Anonymous> -> winch_call -> <Anonymous> -> winch_trace_back
  Execution halted

P. S. Updating sources is still an improvement, without that it cannot work.