Implement static test for naturaldocs comments

The naturaldocs comments sometimes have wrong name references.
The new static test 'C-kern/test/static/naturaldoc.sh' will
check for that.

Corrected natural doc comments with wrong name refs.

Renamed log_config_MAXSIZE into log_config_MINSIZE which describes
better what it means.
Add -fstack-protector-all to DEBUG build

The Release build adds -fno-stack-protector
utf8scanner_t handles chars split acrosss buffers

The interface of utf8scanner_t was changed.
Instead of starting and ending a token explicitly
scanning the buffer automatically starts a token and
calling scannedtoken_utf8scanner ends the token.

Added new functions to scan for utf8 characters.
Previously only bytes could be read.
If a multibyte sequence is split over two buffers
it is handled correctly.