Feature Request: Add version macros to esp-idf (IDF-253)

[chrta]

To be able to write code that works for multiple versions of esp-idf, it is necessary to detect the version during compile time. Something like the following would be good:

/** X.x.x: Major version of the stack */
#define ESP_IDF_VERSION_MAJOR      3
/** x.X.x: Minor version of the stack */
#define ESP_IDF_VERSION_MINOR      0
/** x.x.X: Patch level of the stack */
#define ESP_IDF_VERSION_PATCH      4

For example this is done in lwip:
https://github.com/espressif/esp-lwip/blob/99d992cac3e9d7614ba30ac75f6df35adb59f2e1/src/include/lwip/init.h#L53