Use cabal properly for backend
Clean up unused or rarely used macros
Add OP1 and OP21 macros
Remove observation opcodes from frontend
Rename OP to OPFUNC, add OP, divide ops into sections
Be more consistent about macro capitalisation
Fix off-by-one bug in assert
Move write_force() to syscalls.c
Remove old comment
Incorporate dmbarbour's parsing changes
Stop running tests on SIGINT
Perform proper error handling in parser
Remove unused definitions
Remove unused Type datatype
Fix -Wall warnings
Fix hlint warning
Turn on -Wall for ghc
Pass -Wextra to Clang