Split code generation from the ui

TODO

@@ -4,14 +4,15 @@
 - Make writing ELF independent from the code generation.
 - Argument parsing.
 - Whitespaces are checked twice, in the source class and by lexing.
-- Replace pointer and length with vectors and strings.
-- Choose one name for runner.cpp and tester.hpp.
-- Move argument handling into the cl module.
 - Catch exceptions thrown by the argument parser and print them normally.
-- cmake clean target.
 - Division.
 - Expressions contain one or more terms. Currently it parses another expression on the right side.
 - Multiple factors.
+- Put riscv code into the backend namespace.
+- Rename riscv backend structs to be snake case.
+- Make reference and Target be nested types of the visitor.
+- Rename visitors to snake case.
+- The backend visitor seems to generate code before the prologue.
 
 # Shell
 - Persist the history.
@@ -30,8 +31,3 @@
 
 - Add a bar with additional information under the prompt (edit_bar), like the hostname.
 - Show current time in the prompt.
-
-## Input
-
-- DEL handling.
-- Starting long running process and killing it with Ctrl-C kills the shell.