included-tests: generate binary data from test files for inclusion into test binaries

This change moves test data into the binaries rather than reading them from
the disk at runtime.

Advantages:

• Tests become distributable
• Cross-compile friendly. Build on one machine and execute in an arbitrary location on another.
• Easier testing for backports. Users can verify that tests pass without having to track down corresponding test data.
• More trustworthy test results and easier quality assurance as tests make fewer assumptions about their environment.
• Tests could theoretically run at client/daemon startup and exit on failure.

Disadvantages:

• Required 'hexdump' build-dependency. This is a standard bsd tool that should be usable everywhere. It is likely already installed on all build-machines.
• Tests can no longer be fudged after build by altering test-data.