Teensyduino 1.53

Changes since 1.52

Support for Arduino 1.8.13
Reduce EventResponder and yield() overhead (KurtE)
Audio design tool checks I/O compatibility (thanks to Frank's JavaScript work)
Update audio design tool documentation
Speed up ILI9341_t3 and add setClock (Larry Bank)
USBHost_t36 add Keyboard attachRawPress & attachRawRelease (David "plugz")
Fix DmxSimple on Teensy 4.0 (Adam Demuri)
add pgmspace.h (not avr folder) compatability for Teensy 4.0
minor updates to SD and Wire examples
Improve C++ STL support
Fix compiler warnings in several library examples
Update libraries: FastLED, MIDI, RA8875, Adafruit_NeoPixel, FlexCAN, FlexCAN_T4, ILI9488_t3
Entropy library support for Teensy 4.x random number hardware
ILI9341_t3 proportional font rendering speedup (Larry Bank)
Audio: add rectifier effect and vocoder example by Bradley Sanders
Fix serialEventUSB1 & serialEventUSB2 on Teensy 4.x (KurtE)
Add MIDIUSB.h compatibility on Teensy 4.x
Check hardware serial FIFO in avalable and peek (KurtE)
Remove libraries: Adafruit_GFX, Adafruit_CC3000, Adafruit_RA8875, openGLCD, ST7565
Add SPI.end() on Teensy 4.x (KurtE)
Fix PT8211 output on Teensy 4.x
Fix USB BDT clear at startup on Teensy 3.x (Memotech-Bill)
Add digitalToggle(pin)
Fix numerical overflow in Audio CPU usage on Teensy 4.x
Remane addStorage to addMemory
Add Teensy 3.5/3.6 hardware random to Entropy (Manitou)
Fix ILI9341_r4 readcommand() & add readScanLine() on Teensy 4.x
Installer will delete old/stale libraries
Linux installer checks udev rules
Libraries updated: ADC, ILI9488_t3, RA8875
Fix audio library on Teensy LC
Fix ST7735_t3 spitftbitmap example (KurtE)