The new message is:
"Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace."
1. In crash logs we used to print a message which points to the llvm bug tracking page. Now it points to the swift.org bug tracking guidelines.
2. Use the same message in all compiler diagnostics which ask the user to file a bug report.
rdar://problem/70488534
VS2015 had an issue with the deletion of an operator. Since VS2017 is
the minimum version that LLVM uses, we can assume that VS2017+ is in use
(_MSC_VER >= 1910). Clean up the now defunct workaround.