apache: multiple vulnerabilities

- CVE-2015-0253 (denial of service): Fix a crash with ErrorDocument 400 pointing to a local URL-path with the INCLUDES filter active, introduced in 2.4.11. PR 57531.

- CVE-2015-3183 (denial of service): core: Fix chunk header parsing defect. Remove apr_brigade_flatten(), buffering and duplicated code from the HTTP_IN filter, parse chunks in a single pass with zero copy. Limit accepted chunk-size to 2^63-1 and be strict about chunk-ext authorized characters.

- CVE-2015-3185 (authentication bypass): Replacement of ap_some_auth_required (unusable in Apache httpd 2.4) with new ap_some_authn_required and ap_force_authn hook.