SSA Based compiler targeting x86_64

Code structure:

• buffer.h contains buffer utils, dbuffer_t range position_t etc.
• format.h text formating, similar to printf but can output into a dbuffer.
• hashmap.h separate chaining hashmap, intrusive, doesn't do many allocations.
• ir.h IR definition and utils.
• zone_alloc.h, a bump pointer allocator. Useful for storing a entire data structure.
• dot_builder.h builds a GraphViz dot file, very useful.
• dominators.h dominator tree and dominance frontier calculation.
• x86_64_assembly.h encoder for x86_64 assembly.
• parser.h/parser.c AST definition and recursive descent parser.
• ir_creation.h creates non-SSA IR from AST, SSA conversion happens later.
• ssa_conversion.h is the code for converting non SSA IR to SSA
• elf.h elf file handling.
• platform_utils.h allocating executable memory. used for JIT execution.
• relocation.h used for linking.