Added iris_ prefix to all functions

Prevents conflicts with ncurses and other libs
Added dbg.c - the main debugger code
Added a .gitignore
Removed dependencies on ncurses for dbg

Ncurses is interesting but a simpler design is best.
The debugger does basic stepping now

- you can quit and continue (although you can't get out of continue at this
  point)
Updated install and uninstall
Updated test_mnemonic and test_unparse
Added push and pop commands

- Also added an iris_rom_init command to cut down on duplicated code in tools
sim, img, and dbg now use iris_rom_init
Added push and pop support
Fixed the stack so that index zero is used correctly

- The index during a push is incremented first and that address is used.
- When performing a pop the address is decremented after extracting the current
  value.
Added push and pop to the assembler