lib/mp-readline: Add n_chars argument to mp_hal_erase_line_from_cursor.

If VT100 support is not available then a given implementation of
mp_hal_erase_line_from_cursor might need to know the number of characters
to erase.

This patch does not change generated code when VT100 is supported, since
compiler can optimise away the argument.

lib/mp-readline/readline.c

@@ -82,7 +82,8 @@ STATIC void mp_hal_move_cursor_back(uint pos) {
     }
 }
 
-STATIC void mp_hal_erase_line_from_cursor(void) {
+STATIC void mp_hal_erase_line_from_cursor(uint n_chars_to_erase) {
+    (void)n_chars_to_erase;
     mp_hal_stdout_tx_strn("\x1b[K", 3);
 }
 #endif
@@ -338,8 +339,7 @@ delete_key:
     if (redraw_from_cursor) {
         if (rl.line->len < last_line_len) {
             // erase old chars
-            // (number of chars to erase: last_line_len - rl.cursor_pos)
-            mp_hal_erase_line_from_cursor();
+            mp_hal_erase_line_from_cursor(last_line_len - rl.cursor_pos);
         }
         // draw new chars
         mp_hal_stdout_tx_strn(rl.line->buf + rl.cursor_pos, rl.line->len - rl.cursor_pos);

windows/windows_mphal.c

@@ -92,7 +92,7 @@ void mp_hal_move_cursor_back(uint pos) {
     SetConsoleCursorPosition(con_out, info.dwCursorPosition);
 }
 
-void mp_hal_erase_line_from_cursor() {
+void mp_hal_erase_line_from_cursor(uint n_chars_to_erase) {
     assure_conout_handle();
     CONSOLE_SCREEN_BUFFER_INFO info;
     GetConsoleScreenBufferInfo(con_out, &info);

windows/windows_mphal.h

@@ -29,4 +29,4 @@
 #define MICROPY_HAL_HAS_VT100 (0)
 
 void mp_hal_move_cursor_back(unsigned int pos);
-void mp_hal_erase_line_from_cursor();
+void mp_hal_erase_line_from_cursor(unsigned int n_chars_to_erase);