AST Validation

[A1Liu]

• Deleted some old code
• Moved C library code again
• Moved test runner to the test crate
• Moved lexer, macros, and parser to the parser module
• Re-organize derived declarator system to be nested, so that it's easier to ride the parent-pointer chain to the declaration w/ the base type
• Removed print_err from internals of run_compiler, and instead the full error gets returned to the StageOutput
• Made display_tree accept Vec<AstNode> instead of AstNodeVec
• Fixed display_tree to print roots in order instead of reversed order
• Add basic type database system
• Add types for AstDeclarator
• Removed test running for projects that don't really do testing
• Add type display for AST identifier nodes