Add build target to run tests on Flash, JavaScript, etc.

[djcsdy]

Since #11 there is a build target to run our automated tests on Neko.

Unfortunately just because the tests pass on Neko doesn’t mean they will pass on other platforms. Indeed, they are currently failing on Flash.

It’d be really useful to have a build target to run tests on other platforms, although it will be quite a bit trickier.

• For JavaScript we could possibly run tests in node and/or PhantomJS.
• For Flash we could invoke the standalone Flash Player and write a wrapper to report test results back over a socket. FlexUnit’s Ant tasks work this way.
• For PHP we could invoke the php binary if available (if it’s built with CLI support).
• For C# it should be feasible to invoke a C# compiler and then invoke the resulting executable, although it’s likely to be tricky to make this work cross-platform.
• For Java it should be trivial to invoke the Java compiler and run the resulting binary with the JRE, because Ant supports this natively.
• For C++ we could conceivably invoke a C++ compiler and then invoke the resulting executable, but this is almost certainly more work than it’s worth.

[djcsdy]

Split into #14, #15, #16, #,17, #18, #19.