Fix for deprecated features.

[Chris--A]

In the new compiler (4.8.1 - AVR) the prog_* variants (prog_char) are deprecated and removed. Standard types should be used instead (char).

These could be re-activated by adding a compiler option -D for PROG_TYPES_COMPAT.

It appears many people are using libraries/examples which declare these types causing type undeclared errors. It would avoid a lot of headache by simply keeping them in (if the PROGMEM added to the prog_* defines doesn't cause problems).

[facchinm]

Hi @Chris--A ,
we are trying to get rid of all the legacy and deprecated definitions "the hard way" ™ so defining __PROG_TYPES_COMPAT__ could only slow down the adoption of the new ones.

Also, the definition does not automatically solve the compile failure but simply tells to add the keyword const, leaving the deprecation problem opened. Instead, if the library author fixed it "the right way" ™ it would be fixed forever.

However you are right, the error without the #define is cryptic and we should do something more to tell the user a possible solution.

An entry about this topic exists ( https://github.com/arduino/Arduino/wiki/1.6-Frequently-Asked-Questions#errors-related-to-avr-progmem-changes) but it's not easily reachable, so we'll integrate it in the Reference soon.

Cheers!