This commit adds a pair of encoder/decoder to take the advantage of the
BigSize format when encoding an uint64 and possibly an uint32.
Often the time an uint64 value is not big enough to fill all the 8
bytes, thus using BigSize can save extra bytes when save it to db. And
for uint32, if we know most of the values do not exceed 65536, we can
also save at least 1 byte using BigSize format.
This commit introduces `MakeBigSizeRecord` that can be used optionally
where db space is a concern.
This commit was previously split into the following parts to ease
review:
- 2d746f68: replace imports
- 4008f0fd: use ecdsa.Signature
- 849e33d1: remove btcec.S256()
- b8f6ebbd: use v2 library correctly
- fa80bca9: bump go modules
This commit adds concrete encoding methods for primitive integral types.
When external libs need to create custom encoders, this allows them to
do so without incurring an extra allocation on the heap. Previously, the
need to pass a pointer to the integer using an interface{} would cause
the argument to escape, which we avoid by having them copied directly.
