PR52981: mod_request: fix check for bad KeptBodySize argument

Add lots of unique tags to error log messages

Consistently use base 10 for numbers when parsing config options. It may be confusing to the user if some directives treat a number with leading zero as octal while most don't.

Expose "new" ap_parse_form_data() function instead of requiring mod_request for any module that may want to parse form data...

Fix some compiler warnings: - suggest braces around empty body in an 'if' statement - comparison of unsigned expression >= 0 is always true - comparison of unsigned expression < 0 is always false Please review carefully.

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

mod_request: Make sure the KeptBodySize directive rejects values that aren't valid numbers.

Remove trailing whitespace from the mod_request module.

You don't export the fn hooked or registered as an optional fn

mod_request: Insert the KEPT_BODY filter via the insert_filter hook instead of during fixups. Add a safety check to ensure the filters cannot be inserted more than once. [Graham Leggett, Ruediger Pluem]

* Make code more readable by using OR (which is also Roys preference over AND) instead of XOR.

Fix the optional declarations so that the modules will build clean in a mod_so environment.

Move the KeptBodySize directive, kept_body filters and the ap_parse_request_body function out of the http module and into a new module called mod_request, reducing the size of the core.