tests: use the ORC_STATIC_OPCODE_FLOAT flag to simplify the tests
accumulator: use the local variable 'var'

The code already had the local var, but barely used it.
docs: hook up generate_table tools

Add a makefile-target in docs to update the tables (for a release). Emit a
comment at the top of the generated files which tool produces them so that
people don't edit them manually.
docs: add more opcode descriptions