Initial commit: WAFER (WebAssembly Forth Engine in Rust)

Optimizing Forth 2012 compiler targeting WebAssembly with IR-based
compilation pipeline, multi-typed stack inference, subroutine threading,
and JIT/consolidation modes. Rust kernel with ~35 primitives and Forth
standard library for core/core-ext word sets.

forth/core_ext.fth

@@ -0,0 +1,11 @@
+\ WAFER Core Extensions Word Set
+\ Forth 2012 Section 6.2
+
+\ TODO: Step 13 - Implement as compliance tests are enabled
+\ : VALUE     CREATE , DOES> @ ;
+\ : TO        ' >BODY ! ;
+\ : DEFER     CREATE ['] ABORT , DOES> @ EXECUTE ;
+\ : DEFER!    >BODY ! ;
+\ : DEFER@    >BODY @ ;
+\ : IS        STATE @ IF POSTPONE ['] POSTPONE DEFER! ELSE ' DEFER! THEN ; IMMEDIATE
+\ : ACTION-OF STATE @ IF POSTPONE ['] POSTPONE DEFER@ ELSE ' DEFER@ THEN ; IMMEDIATE