We were consuming all whitespace from the format, but not the input
lexer - that was left to the actual format parsing code. It so happened
that we did not account for whitespace with the conversion specifier
'[', causing whitespace to end up in the output variables.
Fix this by always consuming all whitespace and removing the whitespace
logic from the conversion code.
This was currently crashing Half-Life because it was a considered an
"Unknown" specifier. We can use the same case statement as the regular
hex format conversion (lower case 'x'), as the backend
to convert the number already supports upper/lower case input, hence
we get it for free :^)
Also add a test to prevent this from happening again. There were two
bugs:
* The number of bytes just after processing the last value was written,
instead of the number of bytes after skipping remaining whitespace.
Confirmed by testing against GNU's `scanf()` since the man page
leaves something to be desired.
* The number of bytes was written to the wrong variable argument; i.e.
the first argument was overwritten.
