fixes for building on windows/msys2

[giuspen]

• version locally the script geany-plugins-release.py so far hosted in the wiki
• applied fix for building without signing (missing key/certificate in the filesystem)
• applied fix to geanygendoc/docs/Makefile.am
• applied fix to lsp/src/lsp-server.c
• applied fix for languages binaries not being generated
• changed version num to 2.1

[b4n]

Could you please split each item to its own commit? We prefer having smaller more specific commits leading to the final stage. Of course each commit should be complete in regard of what it is meant to achieve, but each of these should try and be small. It also gives you the opportunity to actually explain why you changed something, both to help reviewers and future understanding of why a change has been made.

[eht16]

Is this change on purpose?

If so, @techee should add it upstream as well.

[techee]

No problem to add but is it actually needed @giuspen ? The plugin seemed to build without it on my machine at least.