Clean up size_t abuse, part 2. ap_malloc/calloc/realloc are explicitly excluded from this cleanup as they must be signature identical to the clib functions, and although the definition of size_t has been flakey, the definition of those functions appears to be generally clean since ANSI C.

Add lots of unique tags to error log messages

Introduce ap_(get|set)_core_module_config() functions/macros and use them everywhere. We know that the core module has module_index 0. Therefore we can save some pointer operations in ap_get_module_config(cv, &core_module) and ap_set_module_config(cv, &core_module, val). As these are called rather often, this may actually have some (small) measurable effect.

remove more useless use of strlen

Added http_config.h to make APLOG_USE_MODULE macro visible.

Use the new APLOG_USE_MODULE/AP_DECLARE_MODULE macros everywhere to take advantage of per-module loglevels

Fix string constness to get rid of gcc compiler warnings by -Wwrite-strings.

mod_session_cookie, mod_session_dbd: Make sure cookies are set both within the output headers and error output headers, so that the session is maintained across redirects.

mod_session_cookie: Make sure that cookie attributes are correctly included in the blank cookie when cookies are removed. This fixes an inability to log out when using mod_auth_form.

* server/util_cookies.c (ap_cookie_write2): Add missing sentinel in apr_pstrcat call.

Remove all references to CORE_PRIVATE.

Tweaking code to compile on pre-C99 compilers

mod_session_cookie: Add a session implementation capable of storing session information within cookies on the browser. Useful for high volume sites where server bound sessions are too resource intensive.