Add input statements, put_char and space

v0.10

Add 'space' statement

Generalize data statements

Allow 8-, 16-, 32- and 64-bit values -- and complex expressions as long as
they are assembly time constants. An error is signalled if the assembler
is not able to reduce the expression to a constant.

Add *-notation and increase initial stack size

v0.8

Add *-notation as sugar for !!..!

Add video output

v0.7

Add video output

Run with "argument file"

Append arg and initial stack (16) in the executor

This is how the machine will be started in the iVM project.

Add support for assembling multi-file projects

v0.5

Add support for depencies between source files

Improve trace output

v0.4

Improve trace output (show labels, etc.)

Add call, return and EXPORT, and fix bugs

v0.3

Show exported labels when running as-trace

v0.2

Small, but important bug fix.

v0.1

Include usage in readme