Non terminal cannot have string aliases (only tokens appear in error

Non terminal cannot have string aliases (only tokens appear in error
messages).  %token is used to define tokens, and %nterm non terminals.
The hidden %type (which was only recently documented) is meant for
both tokens and non terminals.  Yet

    %type <foo> expr "expression"

is actually more or less equivalent to

    %nterm <foo> expr
    %token <foo> "expression"

which is clearly not the intention of the author here.

* server/util_expr_parse.y: Remove useless string-literal only tokens.
Prefer %nterm to %type to avoid this error.

PR: #72
Submitted by: Akim Demaille <akim.demaille gmail.com>

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1869724 13f79535-47bb-0310-9956-ffa450edef68