Release 5.5.0 (NNCP)

Bugfixes in nncp-call(er)/nncp-daemon, nncp-bundle and nncp-stat.
nncp-rm has -dryrun and -older options now.
nncp-exec has -use-tmp and -nocompress options now. Uncompressed packets are not compatible with previous NNCP versions.
nncp-call, nncp-caller and nncp-daemon commands have -autotoss* options for running tosser after call is ended.
Updated dependencies. Minimal required Go version is 1.12.