Implement division

TODO

@@ -1,18 +1,13 @@
 # Compiler
 
-- Separate headers and sources for the compiler, shell and tests.
-- Make writing ELF independent from the code generation.
-- Argument parsing.
 - Whitespaces are checked twice, in the source class and by lexing.
 - Catch exceptions thrown by the argument parser and print them normally.
-- 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.
+- Parser should be able to collect errors.
+- Provide position information on parse tree nodes.
+- Move constants to the symbol table, so we can check at parse time for duplicates.
+- Allow defining variables.
+- Don't pass raw pointers to the visitor methods.
+- Make error abstract and derive unexpected_token in the lex module from it.
 
 # Shell
 - Persist the history.