For fixed-width character displays like LCD1602, custom width would be ignored; for graphical displays like MAX7219-LED-matrix and SSD13xx OLED displays, could specify the character's width
Available number of characters will be display-specific: 8 for HD44780 (using CGRAM); 127 or 128 for those that rely on CowPi_stdio to provide the font stored in microcontroller's SRAM or flash
Return the character value instead of allowing it to be specified
Returns NUL if no character value is available
Complementary functions:
remove custom character (to make room for another)
add custom character from CowPi font (mainly useful for HD44780)
xxx_P option for AVR platforms to use character descriptions in flash memory
NULif no character value is availableComplementary functions:
xxx_Poption for AVR platforms to use character descriptions in flash memory