Add OPJ_VERSION_MAJOR, OPJ_VERSION_MINOR, OPJ_VERSION_MICRO macros in openjpeg.h

[rouault]

Currently for code using openjpeg.h, it is not possible to kow, at compile time, which version of openjpeg is used. Such information can be useful in case of API changes (or behaviour changes that doesn't reflect in the API) to have a code base working against several versions.
Macros (#define) that would hold this information would be useful to do things like

#if OPJ_VERSION_MAJOR > 2 || (OPJ_VERSION_MAJOR == 2 && OPJ_VERSION_MINOR >= 2)
....
#endif

[rouault]

Actually this is not indeed. A opj_config.h file exists with that information and is already installed in include/