Release 0.4.2: Graphics and plotting

New features:
- Display folder marker on directories in VariablesMenu (#309)
- Alternate menu styles (sqare vs. rounded, single-line or 3-line) (#310)
- `line`, `circle`, `ellipse`, `rect` and `rrect` graphic commands (#311, #316, #318)
-  `linewidth`, `foreground`, `background` graphic commands (#312)
- `ppar` special variables for user coordinates (#319)
- `cllcd` to clear the screen
- `drax` to draw plotting axes (#321)
- `draw` command to plot a function (#323)
- `wait` command to wait for a delay or key press (#324)

Bugs:
- Memory corruption when GC was triggered in a constructor (#325)
- Improve `complex_promotion` to avoid undesirable complex format changes
- Wrong pattern alignment in screen blitting operations
- Off by one error in width and height of blitter rectangles (#
- Conversion of fractions to uint32 (#321)
- Conversion between `bignum` and `uint32` / `int32`

Improvements:
- Update `dmcp` commit to include a single fix for `_exit`
- Better rendering of folder menus, looks more like a folder (#310)
- Add .clang-format file to facilidate standard code formatting
- Add AUTHORS file
- Global variable lookup is now case-independent

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

src/qspi_crc.h

@@ -1,4 +1,4 @@
 
-#define QSPI_DATA_SIZE  1522780
+#define QSPI_DATA_SIZE  1524284
 #define QSPI_DATA_CRC  0x000cfed6