mark core as nostd

* implement custom hashmap to back symtable
* pass in print and read callbacks to keep stdlib pure
* use core / alloc versions of Box, Rc, Vec, etc
* replace pow func with libm

Signed-off-by: Ava Affine <ava@sunnypup.io>

core/src/stl/boolean.rs

@@ -18,7 +18,9 @@
 use crate::segment::{Ctr, Seg, Type};
 use crate::error::{Traceback, start_trace};
 use crate::sym::{SymTable, ValueType, Args, Symbol};
-use std::rc::Rc;
+use alloc::rc::Rc;
+use alloc::boxed::Box;
+use alloc::string::{String, ToString};
 
 const AND_DOCSTRING: &str =
     "traverses a list of N arguments, all of which are expected to be boolean.