The old lib.opcodes bindings had a way to detect, at runtime, that there wasn't
a disassembler.  The testsuite used that to skip (mark as unsupported)
disassembler tests.  The new bindings lack this (they throw an exception which
could be caught?).

This will let us correctly fix tests such as:

public class TestDisassemblerCommand extends TestLib {
    public void testHpdDisassemble() {
        if (unsupported("disassembler", true))
            return;

to instead be:

    public void testHpdDisassemble() {
        if (missingDisassembler())
            return;

Where frysk.junit.TestCase.missingDisassembler(), modeled on missing32and64(),
would report UNRESOLVED on IA-32 and x86-64 where there should be a
disassembler, but UNSUPPORTED on PPC where the disassembler is simply missing.