ruTorrent v5.1.11

This hotfix resolves compatibility with rTorrent v0.15.2+.

What's Changed

• Add text/xml content type to xmlrpc request header by @rozhuk-im in #2911
• Remove invalid API 11 command mappings by @rozhuk-im in #2910

Full Changelog: v5.1.10...v5.1.11