pyexec: Handle a ctrl-c that comes in "very late"

In relatively unusual circumstances, such as entering `l = 17 ** 17777`
at the REPL, you could hit ctrl-c, but not get KeyboardInterrupt.
This can lead to a condition where the display would stop updating (adafruit#2689).

Author: jepler

lib/utils/pyexec.c

@@ -113,6 +113,8 @@ STATIC int parse_compile_execute(const void *source, mp_parse_input_kind_t input
         start = mp_hal_ticks_ms();
         mp_call_function_0(module_fun);
         mp_hal_set_interrupt_char(-1); // disable interrupt
+        // Handle any ctrl-c interrupt that arrived just in time
+        mp_handle_pending();
         nlr_pop();
         ret = 0;
         if (exec_flags & EXEC_FLAG_PRINT_EOF) {