v0.0.5

Various development towards an initial release.

I'm pretty happy with where the language and runtime library is now. There's a few loose ends to tidy up, but it's getting pretty close to a basic 1.0.

Change list:

• Increase default heap to 4MB.
• Fix several garbage collector bugs.
• Fix text rendering when transparent colour is not 0.
• Allow `!`, `==`, `&&`, `||` as alternatives to `not`, `=`, `and` and `or`.
• Declare variables in nested blocks. (No scoping rules yet, var is still visible outside the block).
• Declare variables in `for` statements.
• New runtime functions:
• `frac` function to get the fractional part of a float.
• `atan2`
• `srnd` (seed random # generator)
• `interval` timing function
• Use cross-platform random # generator.
• Load and play .wav files.
• Structure forward declaration.
• `flipx` and `flipy` params for `drawimg`.
• Dynamic length arrays (see `.add` and `.remove` array methods).
• Multi-line string literals.
• Various bug fixes.