Linker Implementation

[jackwthake]

The goal of this branch is to implement a linker that merges compiled ir object files into one ir file that can then be passed to the code generator, c02-as

foo.c02 ─► c02-frontend ─► foo.o ─┬► c02-ld (Ocaml based linker and optimizer) ─► prog.o ─► c02-as ─► prog.bin
bar.c02 ─► c02-frontend ─► bar.o ─┘

I'm choosing to do this in Ocaml because I want to learn it and the strict typing will be useful

[jackwthake]

Whats left before merge:

• struct dedup - currently struct decls across multiple modules just concatenate. Need to ensure same layout -> emit 1 else -> error
• missing main function check - currently checks for redefined mains but not missing main
• re-serialize linked object for codegen phase
• add test suite for linker cases

[jackwthake]

Great work Jack!