Update from 1.14.0 to 1.15.0.

<ChangeLog>

*) Change: extensions of dynamically requested PHP scripts were

restricted to ".php".

*) Feature: compatibility with Ruby 2.7.

*) Bugfix: segmentation fault might have occurred in the router process

with multiple application processes under load; the bug had appeared
in 1.14.0.

*) Bugfix: receiving request body over TLS connection might have

stalled.

</ChangeLog>