Caseless location tree construction (ticket #90).

Caseless location tree construction (ticket #90).

Location tree was always constructed using case-sensitive comparison, even
on case-insensitive systems.  This resulted in incorrect operation if
uppercase letters were used in location directives.  Notably, the
following config:

    location /a { ... }
    location /B { ... }

failed to properly map requests to "/B" into "location /B".