Extend assembler & build process for better integration

-- add a step that converts assembly EQU/BSS files to Forth Constants files
-- move symbols around
-- add ASSERT directive to verify RAM bounds
Fix assembler operand precedence
Renaming to split standalone vs. ROM-hosted FORTH
Clean up confusion about the way interrupts work
More work on enabling interrupts in Forth banked ROM
Integrate terminal / video setup & EMIT into ROM
Fix standalone build execution
Fix bug with reentrant XOP+interrupt, try and don't use TYPE in XOP (due to memory read!)
Tighten up LIMI 0 usage and preservation of F_BANK1 to actually fix the bug mentioned before