[Bug libstdc++/62258] uncaught_exception() equals to `true' after rethrow_exception()

[dprokoptsev at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62258

--- Comment #2 from Dmitry Prokoptsev <dprokoptsev at gmail dot com> ---
Created attachment 33395
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33395&action=edit
Proposed patch

I believe the problem is that std::rethrow_exception() does not update
`__cxa_eh_globals::uncaughtExceptions' (which remains zero), while
__cxa_begin_catch() decrements it to -1.

A proposed patch is attached.