raddbgi_from_pdb: multithread initial independent parsing/preparation phases of converter

src/base/base_thread_context.h

@@ -23,6 +23,7 @@ struct TCTX
 // NOTE(allen): Thread Context Functions
 
 internal void      tctx_init_and_equip(TCTX *tctx);
+internal void      tctx_release(void);
 internal TCTX*     tctx_get_equipped(void);
 
 internal Arena*    tctx_get_scratch(Arena **conflicts, U64 count);