Add binary input/output functions

[xanderio]

This extension seems to only support text input/output, and lacks binary input/output (receive/send) functions. Binary transfer would make transfer much more efficient on these types of values, and would make the extension usable in a wider range of contexts. For example sqlx which only supports binary transfer. See issue launchbadge/sqlx#1480 and launchbadge/sqlx#1269.

[theory]

Happy to merge a pull request that adds send and receive functions. I assume that sqlx is unable to handle any types without send and receive, like ltree, yes?

[abonander]

What would be a good binary format? Something like (in Postgres Message Data Types):

Int64 majorVersion
Int64 minorVersion
Int64 patchVersion
String prerelease

[theory]

The most portable is probably to pack them into a char string, literally the ascii bytes that make up a semver. Might also eventually end up as the internal representation, too (see extensive discussion in #47).

[abonander]

Yeah, that was the alternative I already had in mind.

[theory]

v0.32.0 now released and on PGXN with support for binary input and output.