WIP. Continue working on parser.
Get parser working and add some test cases for it.
Merge branch 'dev'

Conflicts:
	src/parser.c
Reorganize parser code.
Merge branch 'master' of https://github.com/butchler/PL0-compiler
Reorganize the parser code some more, and add a full PL/0 grammar test case.
Merge branch 'dev'

Conflicts:
	src/parser.c
Merge branch 'master' of https://github.com/butchler/PL0-compiler
WIP. Trying to add expressions to code generator.
Add expressions to code generator and add test cases for them.
WIP. Trying to clean up code generator code.
WIP. Trying to improve parser error messages.
WIP. Stupid lisp stuff.
Merge branch 'master' of https://github.com/butchler/PL0-compiler
Merge branch 'master' of https://github.com/butchler/PL0-compiler
Simplify and finish code generator

Simplify the code in the code generator a bunch and add
const-declaration, while-statement, and assignment to it, to finish it.
Merge branch 'master' of https://github.com/butchler/PL0-compiler
Merge branch 'dev' of https://github.com/butchler/PL0-compiler into merge

Conflicts:
	src/parser.c
	src/parser.h
	test/test.c
Forgot to enable assignments in code generator.
Add compiler program.