Add soversion to the library build.

[xelageo]

This add a soversion to the libhexagonrpc, allowing easier upgrade when changing the ABI and would allow a much more standard way to package it in debian.
Meson will generate libhexagonrpc.so.0 and symlink to libhexagonrpc.so
A working debian package with the patch is available at https://salsa.debian.org/xela/hexagonrpc/-/blob/debian/latest/

[flamingradian]

Could this be done instead with the version argument and the version of HexagonRPC? Breaking changes could happen between 0.3.0 and 0.4.0.

[xelageo]

Sure, I added a version variable in the main meson.build, and use it as parameters for the lib soversion.
Now the build output a libhexagonrpc.so.0.3.2 and its symlink to libhexagonrpc.so.

[flamingradian]

Blank line above this one, just because the project() line needs to be at the top, and the variable doesn't need to be.

Other than that, LGTM (commits will be squashed).

[xelageo]

I added the blank line. Would you like I squash them in my PR branch or GitHub does it automatically ?

[flamingradian]

I'll squash them manually so I can still sign the commit. Your authorship will be preserved.