Use 'ap_request_has_body()' instead of duplicating its implemenation.

The logic in 'ap_request_has_body()' is:
    has_body = (!r->header_only
                && (r->kept_body
                    || apr_table_get(r->headers_in, "Transfer-Encoding")
                    || ( (cls = apr_table_get(r->headers_in, "Content-Length"))
                        && (apr_strtoff(&cl, cls, &estr, 10) == APR_SUCCESS)
                        && (!*estr)
                        && (cl > 0) )
                    )
                );
So the test is slighly different from the original code. (but this looks fine to me)

This also has the advantage to avoid a redundant call to 'apr_table_get()' and to improve readability.

While at it, move the test '!r->expecting_100' a few lines above because it is cheap.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1827374 13f79535-47bb-0310-9956-ffa450edef68