Reverse #13034

It has been found that #13034 was flawed and caused regression #13867.
This patch reveres the changes made by it except the companion tests.
Adjust codegen logic for range and guarded arms

By carefully distinguishing falling back to the default arm from moving
on to the next pattern, this patch adjusts the codegen logic for range
and guarded arms of pattern matching expression. It is a more
appropriate way of fixing #12582 and #13027 without causing regressions
such as #13867.

Closes #13867
auto merge of #13940 : edwardw/rust/refutable-match, r=pcwalton

By carefully distinguishing falling back to the default arm from moving
on to the next pattern, this patch adjusts the codegen logic for range
and guarded arms of pattern matching expression. It is a more
appropriate way of fixing #12582 and #13027 without causing regressions
such as #13867.
    
Closes #13867