py: Free non-interned strings in the parser when not needed.

mp_parse_node_free now frees the memory associated with non-interned
strings.  And the parser calls mp_parse_node_free when discarding a
non-used node (such as a doc string).

Also, the compiler now frees the parse tree explicitly just before it
exits (as opposed to relying on the caller to do this).

Addresses issue #708 as best we can.

1 files changed, 1 insertions, 0 deletions

diff --git a/py/compile.h b/py/compile.h
index 52c42aff4..983a443e9 100644
--- a/py/compile.h
+++ b/py/compile.h
@@ -33,4 +33,5 @@ enum {
     MP_EMIT_OPT_ASM_THUMB,
 };
 
+// the compiler will free the parse tree (pn) before it returns
 mp_obj_t mp_compile(mp_parse_node_t pn, qstr source_file, uint emit_opt, bool is_repl);