lib/src: white space edits to comply better with code style

... as checksrc now finds and complains about these.

Closes #14921

misc: general C style cleanups

... in code that previously was not checksrc'ed

Closes #14625

scripts: add schemetable.c

This tool generates a scheme-matching table.

It iterates over a number of different initial and shift values in order
to find the hash algorithm that

scripts: add schemetable.c

This tool generates a scheme-matching table.

It iterates over a number of different initial and shift values in order
to find the hash algorithm that needs the smallest possible table.

The generated hash function, table and table size then needs to be used
by the url.c:Curl_getn_scheme_handler() function.

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