bitcoin-utils: Fix parsing of of CompactSize integers
When the first byte is greater or equal to 0xfd, (bex len) bytes are consumed to
form the csiz atom, but only one byte is dropped from the 'rest' of the input.
The parser should consume all bytes of the CompactSize.
%0xfe 2
%0xff 3
==
- :_ (drop:byt (add 1 len) h)
+ :_ (drop:byt (add 1 (bex len)) h)
%- flip:byt
(take:byt (bex len) (drop:byt 1 h))
:: +dea: atom instead of hexb for parsed CompactSize
