Alias regex use causing core dump as of nginx 1.7.1

[Per Hansson]

Hi, after upgrading from the v1.6.3 to v1.8.0 stable branch an alias I used
for Roundcubemail no longer works.
I traced the issue back to a probable change made in nginx v1.7.1:
"Bugfix: the "alias" directive used inside a location given by a regular
expression worked incorrectly if the "if" or "limit_except" directives were
used."

In version 1.6.3 and 1.7.0 the following works fine:
        ## Roundcubemail for Remi repository
        location ~ ^/mail/(.+\.php)$ {
           alias /usr/share/roundcubemail/$1;
           client_max_body_size 5M;
           fastcgi_pass _php;
        }
        location ~ /mail {
           alias /usr/share/roundcubemail/;
           client_max_body_size 5M;
           try_files $uri $uri/ /index.php;
        }

But in v1.7.1 it causes nginx to core dump if I visit the url
domain.com/mail and if I visit domain.com/mail/ I get taken to the front
page.

[notice] 26221#0: signal 17 (SIGCHLD) received
[alert] 26221#0: worker process 26223 exited on signal 11 (core dumped)
[notice] 26221#0: start worker process 26231
[notice] 26221#0: signal 29 (SIGIO) received

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,260558,260558#msg-260558