Log message:
parallel: Replace RMD160 checksums with BLAKE2s checksums

All checksums have been double-checked against existing RMD160 and
SHA512 hashes

Log message:
parallel: Remove SHA1 hashes for distfiles

Log message:
parallel/fastflow: Replace bash in scripts

Log message:
parallel/fastflow: import fastflow-3.0.0

FastFlow: high-performance parallel patterns and building blocks in C++

FastFlow is a programming library implemented in modern C++ and
targeting multi/many-cores (there exists an experimental version based
on ZeroMQ targeting distributed systems). It offers both a set of
high-level ready-to-use parallel patterns and a set of mechanisms and
composable components (called building blocks) to support low-latency
and high-throughput data-flow streaming networks.

FastFlow simplifies the development of parallel applications modelled
as a structured directed graph of processing nodes. The graph of
concurrent nodes is constructed by the assembly of sequential and
parallel building blocks as well as higher-level easy-to-use
components (i.e. parallel patterns) modelling typical schemas of
parallel computations (e.g., pipeline, task-farm, parallel-for,
etc.). FastFlow efficiency stems from the optimized implementation of
the base communication and synchronization mechanisms and from its
layered software design.