function prototypes, spelling
Protect AVR specific code by checking for __AVR__

Rather than assuming that everything that isn't an MSP430 is an AVR.
Allows compile on other processors - Arduino Due, Tiva, etc.
PROGMEM - prevent duplicate definitions

Compatability with Energia 13 (which defines progmem in headers)
DEMO2 - Error message rather than number
EPD - const temperature_to_factor
pins -> const uint8_t

Avoid errors with passing negative pin numbers
Clearer that pins can not be changed
EPD_GFX, EPD2_GFX - error if not enough RAM, note need to customize dimension constants
flash_loader, EPD2 - fix warnings - inconsistent arguments to flash_program, signed vs unsigned
Merge pull request #16 from ecdr/misc

Misc - declare constants const, protect AVR specific code by checking for __AVR__
[PlatformWithOS] #17 better initialisation for SPI transfer buffer

Signed-off-by: Christopher Hall <christopherhall.hsw@gmail.com>