* Add smooth arc drawing function
Update ESP8266 architecture reference
Add pushMaskedImage() to render 16bpp images with a 1bpp mask (used for transparent PNG images plus with sprites)
New functions added using drawArc:
drawSmoothArc
drawSmoothCircle
drawSmoothRoundRect
New sqrt_fraction() added to improve smooth graphics performance on processors without a FPU (e.g. RP2040)
Faster alphaBlend() function added which retains 6bpp for green
Rename swap_coord() to transpose()
* Update TFT_eSPI.cpp
* Add arc examples
// For RP2040 processor and 8 or 16 bit parallel displays:
// The parallel interface write cycle period is derived from a division of the CPU clock
// speed so scales with the processor clock. This means that the divider ratio may need
// to be increased when overclocking. I may also need to be adjusted dependant on the
// display controller type (ILI94341, HX8357C etc). If RP2040_PIO_CLK_DIV is not defined
// the library will set default values which may not suit your display.
// The display controller data sheet will specify the minimum write cycle period. The
// controllers often work reliably for shorter periods, however if the period is too short
// the display may not initialise or graphics will become corrupted.
// PIO write cycle frequency = (CPU clock/(4 * RP2040_PIO_CLK_DIV))
//#define RP2040_PIO_CLK_DIV 1 // 32ns write cycle at 125MHz CPU clock
#define RP2040_PIO_CLK_DIV 2 // 64ns write cycle at 125MHz CPU clock
//#define RP2040_PIO_CLK_DIV 3 // 96ns write cycle at 125MHz CPU clock
1. RGB configuration was configured incorrectly, and caused re-definition warnings.
2. MISO pin is not always set, so shouldn't trigger a compilation error (see e.g. `Setup25_TTGO_T_DISPLAY.h`).
