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BACK - A Forth compiler
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I don't know why but I'm writing a Forth compiler now. It's not efficient, the
created assembly code is very bad and un-optimized, I'm directly returning x86
assembly instead of LLVM IR (bc I'm too lazy to learn) but I'm having fun ok ?
Of course, don't use it in production (or anywhere really).
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What is forth ?
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Forth is a stack-based language from the 1970s where everything is written in
reverse-polish notation.

For example, if you want to print the sum of 39 and 3 you would write

	39 3 + .

(The dot is the word for printing the top of the stack)

It's a very simple language to parse and compile. In theory you don't need an
AST since every word can be directly translated to assembly (check the commit
655bd4b for an example).
I want to try making some optimizations so I've made an AST anyway.

But even with its simplicity the language is still very powerful and allows to
abstract and is way easier to write than assembly.

ABI Definition
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| rax | working register  |
| rbx | working register  |
| rcx | Unused for now    |
| rdx | working register  |
| rsi | Unused for now    |
| rdi | Unused for now    |
| rbp | call stack        |
| rsp | call stack        |
|  r8 | working stack top |
|  r9 | do loop i         |
| r10 | do loop max       |
| r11 | Unused for now    |
| r12 | heap top          |
| r13 | Unused for now    |
| r14 | Unused for now    |
| r15 | Unused for now    |